I think other are saying to possibly use rectangular "inside" the wall behind this cabinet that is between your kitchen and DR. If that is the case, I do not think that will work or is necessary. 1st you would have to bend/transition to get that into the wall cavity. You want to eliminate bends as much as possible if you can. Not to mention you will have to take a nice chunk out of the back of the cabinet to accomplish this I would think. Not to mention I think you need something like a 5x12 rectangular duct (narrowest) for the same cubic foot of air movement for an 8" round (according to charts I have seen on the web). This will not fit in the wall. If I am looking at the 2nd photo in your attic correctly, you are saying on the right side on the photo, above the electrical junction box, that is mounted on the joist, is where the hole is located. There is another joist behind it that is the attachment point for the DR ceiling Drywall. There is block on top of the joists connecting the two and there also appears to be horizontal blocking between those 2 joists as well. So again not sure anything could be run inside the wall. If the walls are 2x6 then you have a shot. You said you have 6" from the edge of the joist to the front of the cabinet. So you may be able to transition something here within this space. I brought up Oval duct since it has much better/smoother flow, compared to Rectangular. Also, it would be 3 1/2" width and you should have about 3" now, from the front edge of the circle to where the wire was hanging down. Thus, you would only need another 1/2" of cabinet cut to fit the duct towards the front. But the duct would require you cutting wider.

Rosie: When I was growing up, my mother made me clean my room, help with the cooking, clean the kitchen after dinner and other miscellaneous chores (my mother didn't work). I did not however, mow the grass, scrub the floors, do the grocery shopping, wash the families (6 of us) laundry, help the others with their homework, pay the bills, plant the garden (although I did help weed and pick the vegetables), maintanin the cars and other household appliances. My mother worked very hard at home raising 4 kids while my father worked 12 hours, 7 days a week at Fords to provide for the family. I also went to school and got very good grades, participated in the band and played softball in the summer. At the time, I thought she was the meanest mother in the world, but when I got married at 20, I found out that I had no problem keeping a house, working full time, going to school at night and eventually having children. I was capable of doing all this because my mother prepared me for adulthood. I am very gratefully for that now. Take my stepdaughter for example. I entered her life when she was 15 (she is now 18). She lived with her mother for a few months in the beginning, but decided she preferred to live with her dad and I (and my boys)full time. She did not assist me in any way with anything to do with the house, but was very demanding about being driven here and there and asking for money as if it grew on trees. I asked for her help ie: taking her own dishes off the table and putting them in the dishwasher, etc, and she said she shouldn't have to do that because her mother made her do those things when she was 4 years old. This seemed to be a common excuse which her father and grandmother (who lived with them for 4 years) says did not happen. I didn't want to be a b**chy stepmother , so I didn't press the issue. She was getting good grades in school and was a cheerleader so I figured her time was better spent on those activities. Big mistake!!! She is now 18 and can't even make it out of bed for a 10:00 class at college. She has been late for work many times because she "just slept in" (I can't believe they haven't fired her). Her claim now is that she is 18 and is legally an adult and we cannot ask her to do anything. She began college in September and has now dropped out because she cannot balance, work (20 hrs wk), school 4 classes and socializing with her friends. She demands to be treated like an adult,but was never made to accept any responsibility, so she doesn't know how to act like an adult. I firmly believe that if she had been made to be a part of the family and take responsibility for helping in the running of the household, she would be better prepared for "adulthood". So now we have a disrespectful, inconsiderate, lazy 18 year old in our house that causes a terrible disruption to the rest of the family. How am I supposed to teach my boys how to be proper, respectful, considerate young men when they have an example just the opposite in the household? We have now thrown away $2500.00 in college tuition (which we can't afford) and she has forfeited a $2500.00 MEAP scholarship. What a waste!!! But let's not forget, she has lots of time to socialize with her friends now!!!!! That is really going to get her far in life. Kids need to know that life is not easy and having them help around the house is not going to cause them any harm.

As to being your own GC - one of the biggest values the GC provides is understanding when one sub's changes/requirements impact the next (or previous). ie the plumber needs to change the drain or venting plan b/c of a load baring wall/ducting/joist etc...and that then pushes it too close to the wiring or switch box (so an electrican needs to come in) or the framing needs adjusting (framing carpenter) or the cabinets will need adjusting (cabinet maker). These type of integration questions are really important, and see the issues early is important. You will have great difficulty getting the sub's out for 1 hour jobs, over and over...or they will charge you $$$$. I'm not trying to scare you off of self-GC'ing...lots of people do it successfully ( I do ) but unless you are confident you can see the big picture and how it is impacted from the small details, I would try to find another GC. Just because your first GC experience was poor, does not mean they all are. Caspian

The assessment of trades above by @mackdolan is correct. You’ll need a HVAC person, an electrician, and someone to do drywall. You’ll also need a new dedicated electrical outlet for where you moved your MW. I’m not sure why there isn’t an outlet above the range, where you moved it from, but it wouldn’t be in the right place for a chimney hood if it were. That’s why you have to decide on the hood, and design everything around the exact hood’s specs. The location and shape of the duct and the electrical location is NOT universal. It’s normal to have to move or adjust everything, or do new. You need the specs and the hood on hand when talking to contractors. Don’t forget an exterior damper to keep cold air from infiltrating your home! You will get a better job, done faster, if you hire a General Contractor, rather than trying to hire the trades individually. They have their subs that they give lots of work to, and who will return phone calls and show up. And pull the permits that this will require. A homeowner doesn’t get the same price or response from the trades, and it takes weeks longer. I’d suggest posting on your local NextDoor or Facebook neighborhood or city group to look for a licensed and insured (check this!) contractor who can do a small job. But, it isn’t as small as you think!