At 64 yrs old I just recently received my first credit report. I have either paid off all legit items or successfully disputed the non-legit items. When can I expect my credit score to go back up and by how much? Some of the negative items should never have been there in the first place and have definitely lowered my score needlessly.

As soon as the items are removed/amended, your score will change. By how much we can't say.

I am currently at 573/607/564 before clearing up negative items, but need 620 middle score for mortgage. Is there any reason for me to expect the needed change in the near future? I have VA certificate but need a home/land package first then convert to VA or Rural Development. Any advice at all will be GREATLY appreciated

Tha's close especially on the middle one. But the scoring agency keeps a close handle on the way the formula works, so its hard to predict any actual amounts.