Well, his personality is (or was) more like Reed richards than Tony stark. Not the same, but closer to the genius who is more into science than the guy making sarcastic comments while fighting guys in his armored suit. I like Tony stark (when he's done well) but it just isn't Pym at all.
As for the secret invasion thing, I always read that as the skrull taking over pym probably after Dissassembled, or maybe just
before, but definately not in the 80's. He was replaced awhile after wasp and pym finally broke it off permenantly (from scenes that were shown around the time SI ended), and they were still together during the avengers run that lead to Dissassembled, or atleast still having sex (I know that from a rather disturbing scene in an Avengers issue from the series that ended with dissassembled), but they were definately a couple up until the mid to late ninties, just based off avengers comics I've read from that period where they are definately a couple. So, I think the skrull came in much later than the 80's stuff.