It's getting warm in here.
No appreciable improvement? That's being way too charitable just the opposite. They come out under-informed, overly sensitive, but completely ready to tell everyone else the way things ought to be.
A "4" years old computer can be in good working condition, but in today's Hi-Tech world full of new products coming onto market every year and looking and functioning alot better than a previous version, you needed to reconsider your offer and more especially to whom you were giving. Your "mother inlaw"! She deserves a lot better than this. Even a TV set should be brand new, unless she took initiative to ask for your "OLD" TV set! Sorry fellow man, I am on your girl friend's side. My sympathy goes to her. NOT to you. I expect you to "man up".
I agree, but there's a lot of pressure to build. it's the builders, insurers, and banks that are liable imho. Most people assume (reasonably/unresonably that once the structure is present that it's up to code and meets whatever requirements.