Vintage RCA Projector Big Screen

[stushug]

I have an old RCA projection tv that I've owned since new. It's from 1981, Model PFR-100RW. One of the main reasons it got relegated to non-use was that it was becoming more and more out of focus. There is a built in grid you can use to do a basic alignment, but the focus problem is way beyond what can be corrected that way. What would be the first thing to try bring this set back to life somewhat? I've enclosed some pictures for reference. The mark on the screen has been there for years, caused by the mistaken use of some type of cleaning fluid many years ago.