You need to do a little more archeological digging still. You need to know the whole construction of the floor before you can decide how best to install something new. I'd take up that plywood piece in the kitchen and see what's under it. It's higher than the surrounding floor, so needs to go. You should also be able to see from there what subfloor is under the original kitchen hardwood. It's too bad the space under your entryway is finished, but I'd still do some exploring from below to see what's under there, and to figure out the fix to stop it from squeaking. Is it drywall below or a drop ceiling? I know it probably seems like a pain to tear out drywall, but if you cut out a clean patch, like 2' x the width of the joists, it'll be relatively simple to repair. Just make sure to cut it down the center of the joists so that there's room to screw the patch piece to it later. Cut the hole under the area that squeaks the most, if you can. Have someone walk on and watch the floor from below to see what's moving. It might be as simple as pounding in a couple shims from below, or face-nailing a loose board from above. You want to find out what's underneath the hardwood. It might be laid directly on the floor joists, or there might be 10" wide boards that the hardwood is nailed to. Another thought is to take out a board in the hallway, since that's not original and you want to replace it. See what the subfloor is there. I am a bit puzzled at why, when you've stripped the kitchen down to the original hardwood, it's still higher than the hallway floor. Is your current surface perhaps not the original kitchen hardwood? Peeling back the plywood area will help determine that. BTW, I haven't heard of that stop squeaking product you linked to, so can't offer any personal opinion. And don't pour self-leveling compound over top of hardwood. It needs to go over plywood.

I think Sophie's comments is where things should be looked at much closer. There must be an imbalance of moisture from the basement to second floor. In other words, there are higher Rh levels above the basement causing the crowning. It's usually the other way around where most people complain about cupping that's caused from higher moisture levels from below. (wet basements and crawl spaces) The second level in my view is not as affected as greatly as the first. The two levels are closer in moisture levels, but there's still an imbalance. Of course all this takes time for floors to behave this way, and we're now going into a different season, where the AC will be running. My guess if the RH levels were monitored the last six months or so you’d probably be seeing something like this. I'm using larger numbers just to get a point across. Basement: 15% Rh First Floor: 40% Rh Second Floor: 70% Rh For hardwood floors to function like they’re supposed to or less susceptible to funky appearances, all house levels have to be in some kind of consistent zone of moisture. In Sharon’s case it could have been a matter of plywood sheets separating (a drying condition) and moving in different directions. I’m not the smartest rock in the creek, but after attending an educational session this past week that was put on by the American Plywood Association that looked at issues with solid hardwood floor failures over wood sub floors, I feel smarter. Why doesn't it happen in older homes? Because they’re not insulated to the teeth like the way today’s homes are being built. Moisture is more balanced.

The 'bubbles' look to be debris that has been trapped underneath (a few layers of) the finish. I could be wrong but from the photos it looks more like debris then finish failure. As to removing the 'sealant' (which we call the finish = polyurethane) there is no way to remove just the finish without going past the staining. The work to do this should be pretty easy because most of the work has already been done. If you have debris trapped underneath the finish (again this is just my assumption based on two photos) you can negotiate the price of the redo. If this is adhesion failure (horror of horrors) it will cost you NOTHING. Adhesion failure is 'paid for' by the refinisher. Right now, we know nothing for sure. If you want to change the colour, you will need to negotiate the price. And you will have to FIND OUT what the finish was (Bona is a brand...it isn't the name of the line...we need the name of the LINE of finish) and make sure it is NOT used again. I have a sneaking suspicion the finish is the Bona Mega which is helping turn your floor orange. You will have to confirm this when you speak with the refinisher about the lumps and bumps in the finish. The refinisher is responsible for 'knocking these down'.

I think you take a box of each and lay them out next to yours with your lighting etc so you have a true visual of how they will blend or contrast and to ensure the tones coordinate well. I would get up to 4 options at 1st to work with starting with the closest match to the furthest contrast that you like. Once you have them played out in the patter next to your floors and in your light and the scale of the space it will make a big difference. You will be able time step back and see if from afar, in different times of day etc. Some will stand out right away as the wrong choice, others will take a news days and fighting to decide and narrow it down. Just make sure you can take them back and any time limits for refunds. Try one out at a time. Hope that helps. I also take a picture of things when I first do them and sometimes it helps me pick out changes needed right away. Maybe that is just me but for some reason it is a huge help lol.