Welcome to the forum. The Irwin 34 is supposed to be a quick and spirited boat. That said, I am restoring a '79 and haven't seen the water yet. I don't care as I enjoy working on them as much as sailing them. There are all kind of reviews out there. After 24 years, there is a huge difference in the value and quality of boats made side by side at the factory. I think a well taken care of example could be an excellent value. Yeah, there are some design flaws. Every boat has them. After 24 years you will find they all have issues.
Most of the things you have mentioned are issues on every boat. Granted, the screws are bad news, but they all can be dealt with. check out where the keel attaches to the hull. Other than that, after all this time, the boat choice is kind of a crap shoot. If you like it, get the survey. It will give you some wiggle room for negotiating.
"Ulysses" - Alfred Tennyson