I realize this is way late but I believe you are correct.
I have the same situation so I'm interested on how yours was filed.
Capital gain = 1600K - (300K+300K) = $1000K
Taxable capital gain = $1000K -500K = $500K
Now what is an improvement over 30 years? One exterior paint job? 3 Exterior paint jobs? Bathroom repair?
Maybe an improvement is anything you did NOT have to do. For instance, you don't have to remodel a bathroom or repaint, but you do have to replace a broken water valve (therefore an emergency plumbing repair is probably not an improvement unless you fix it better than new). Thoughts?
