Sorry to hear about all of your problems. You're absolutely right that if the denture doesn't fit it's his mistake and not your fault. You don't say anything about guarantees so I'll have to take your word for it that they promise a replacement if the first doesn't fit. First of all though, you've got some public relations damage control to do. It wouldn't hurt to apologize for getting angry even though you had every reason to be. That should at least smooth out some feathers if any got ruffled. At the very least get back an amicable working relationship with the dentist (you were talking about a dentist right?). I'm going to assume that your denture came from a "chain" clinic such as Affordable Dentures. Threatening them with lawyers probably won't do much good but a letter to the "chain" head office might have some effect. They're a little more concerned about reputation than your average dentist especially if they're a "national" chain. Make sure you send a copy to the offending dentist. If or when you talk to them again try not to lose your cool. If you discuss things with them firmly and matter of factly they'll be more apt to listen and take you seriously. Another thing you can do if it is a "chain" clinic is ask that another dentist be assigned to you. There is a last option you can pursue if $ allow. You can have a new denture made by another dentist or, depending on where you live, a denturist. It's always great to have a spare for emergencies and you'll avoid having to deal with the dentist again.
Where the actual denture is concerned it sounds like the whole thing is a little out of whack, not just the bite. Somehow you're going to have to find a way to demonstrate that the denture and your natural teeth aren't aligning properly. As to why the dentist wanted the denture back, he probably wants to reuse the teeth in order to cut his losses in remaking the denture. I don't think it would be unreasonable for you to refuse if you explain why you need your denture (or ask him if he would like to go without his teeth for a few days
). Your speech problem may be related to the denture being out of alignment. It could also be that you're just one of those people that have a more difficult time with speech while wearing dentures. After 9 months I still can't say my S's consistently from one day to the next but I'm past caring now. I'm not sure what you can do about the "slimey" feel of the denture "gums". To the best of my knowledge most denture acrylics are basically the same. The surface of the acrylic is smooth and the mouth produces saliva so I would expected it to be "slimey" to certain degree. It's common for new denture wearers to produce more saliva than they did before dentures so it may clear up in time.
I hope this has been some help. Good luck in dealing with your dentist. Learning to live with dentures is difficult enough without having a dentist that is difficult too.