Wait, how big is your house that you have 11 empty walls? I read somewhere that the average American home has like 15 to 20 walls total, so that would mean most of yours are bare. Are you counting closet walls and hallways too or just the main rooms? That number seems high unless you just moved in and haven't hung anything up yet.

That bit about him making 3 perfect cuts and the tree dying anyway hits home. I helped my neighbor take down a big limb off his oak two summers ago and we spent like 20 minutes measuring and marking to avoid the collar, then his kid ran over the drop zone with a mower and gashed the trunk. We stood there staring at this clean perfect cut while the real damage was 4 feet below it. Tree healed fine but we learned more from that dumb mower moment than any youtube vid. Now I just focus on not hurting anything around the tree, cuts sorta take care of themselves.