Did he supply the toilet, or did you? If he did, he should make it right at no charge to you. My guess on the tank leak is that he could not get it properly tightened, otherwise, it would have put too much pressure on it. It's also possible that in trying to tighten it with no room, he did crack the tank. BTW, the proper way to attach the bowl is to first tighten the bolts with a rubber washer underneath the head in the tank with a metal washer and nut on the bottom of the tank. This is tightened, then set onto the bowl, and a second washer and nut are used to tighten it to the bowl. Debris in the supply line can happen anytime you shut the water off and then back on again...it's a good idea to flush it, but it may or may not have been an issue long-term. Depending on which Drake you have, it often will fit on a less than ideal flange placement, but it would likely be tough to get a 12" on a real 10" rough-in without issues. Most toilets have some room behind them, some more than others. IMHO, trying to shoehorn a 12" toilet on a true 10" rough-in is like a tire dealer trying to put a 15" tire on a 16" wheel...it just doesn't work 99% of the time, and anyone that has any professionalism would realize that and not give you any grief!