steering box woes

Photo? and brand name? of the puller? You need a good one. I'd get / buy / borrow a good beefy one, get a LOT of tension on the puller bolt and then smack it with a BIG hammer. If you can lift the hammer in your "bad" hand it's not big enough, LOL

If that doesn't work, evaluate "juz how good" the pitman arm really is, and consider just replacing it. They are, after all, a "wear" item