The solution to 1 is to buy a legal copy. The solution for 2 is to reinstall from scratch. The solution for 3 is to get the right patch. The otheer commong snaffu is having DEMOs imbedded in a WAD and having the WAD crash. This either causes the patch to barf, or skip that file.
Solution is to start from a fresh install.
Change the last number to a 9 and you're in business. I don't know from lmp's although I have heard that it's something similar.