There are many thick layers of old paint on the boards and the sanding process may take an eternity.

not to hijack anything, but to me the issue here seems more like the thickness of walls/ ceilings might be too thin ( cheaply built).  

I didn't think to measure the tiles, but I assume they are the 9", about an 1/8th of an inch thick. 

Real estate requires thick skin and its so obvious how easily you are triggered.

What the contractor promised was that he would use jack posts for the support beam and put down two cement columns and then insert a permanent thick wooden or steel beam once the wall was removed and columns set.

Get the same thickness you measured. 

It does scratch irregardless the grade or thickness.

I guess I'm pretty thick headed. 

You have to have thick skin to be a landlord.

My advice would be to replace with carpet, OR require them to have thick area rugs in key areas.