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 had the exact same issue. Initially they thought they could do it. But my house is old and when they did the demo they said the way they did the spacing of the supports under the wood on the older section cannot be duplicated today and the floor would never look even and the old section would always be a little higher and "squeaky". Ended up doing the whole floor. However, the hallways are old hardwood as well and the transition (via a doorway) seems fine.

Exactly. I agree . In my prior comment, the walls are actually pretty square. We measured it in front of him and he also measured. This should not result in a difference of inches on the other side of the room. In my last comment about the rows, I did not measure from wall. I measured from his first row to his last. Which like I sd, we all agreed the walls were fairly even and square. So it’s hard for me to understand how a fairly straight room became off by inches and why there are no expansion gaps on one side of the room to a 3/4in gap. Anyways, he finally admitted to not measuring anything when we asked to see and hear his process/explanation for laying down the floors. All he did was decided to start at the left corner of patio door and that was it. Why he choose the shortest wall in my house to start with patio doors and a fireplace in the center?? Idk. He didn’t have explanation. He blamed my walls for not being squared but how did he know if he never measured? He only measured when my husband and I did it in front of him. He did nothing to ensure his line was straight. No chalk line, no markings, laser, nothing. He said, he’s never had to measure his first row to make sure it’s straight. He also said open concept homes can’t have wood floors that align and flow into other rooms. That you’d have to make rip cuts and lay down transition strips between spaces. I’m sorry, I’m not an expert but I know that statement is untrue. You can flow flooring into other rooms regardless if it’s open space or not. Well an update is we let him go. Our issue still stands. The floors as they enter the other rooms do not match up. At this point, it looks like ripping up the floors the only option. This time, will start in our hallway since that’s our longest wall and it connects all the rooms. Will use splines to switch directions and should there be cuts, it’ll be by the walls and not dead smack in the middle of my floors like it would be now.

Kim,,,it's very solid. just make sure the glue is spread to completely cover the plank. I have a few spots (like under the kitchen sink) where they missed the corner and it squeaks. They've held up great. I don't have dogs, but I have cats and have heard their nails burning rubber across the floor they go off on their tangents. I've spilled water, cleaned up their barf, spilled food, whatever, it all cleans up very well. as for dents, only if you drop something very heavy. but any wood floor will dent. I vacuum w/a Dyson, and then I use Bona wood floor cleaner on a mop. in the kitchen, i'll often take the scrubby brush and watered down Dawn to clean up spills or oil stains. no problem. no, I don't baby them. I don't wear shoes in my house though. I love my floors. just make sure on install they clean up all the glue residue. my guys were messy and lazy. had to call them back w/special glue remover and rag and go over the entire floor.