A few things going on here. My thoughts, in rough order:
Purchase Price - Sounds like you are having some buyer's remorse, second guessing whether the property you already agreed to buy for $415K is actually worth $415K. Regardless of comps, a property is worth what someone will pay. It's probably getting a little late in the game to be worried about that (although see below), you're not overpaying if you decided its worth $415K.
Appraisal - As the buyer seeking a loan, you generally want the appraisal to at least match the purchase price so that you don't have to make up the difference in cash (although there are other ways this can be handled, use the Google). I don't see why you are worrying about the appraisal.
Repairs - I would just seek the $10K from Seller as cash at closing as a portion of closing costs, but there are also different ways to approach this as well. Be ready to negotiate the $10K amount as well.
Finally, depending on where you are in the contract timeline, if the whole deal doesn't feel right you may still have the option to terminate the contract. But from your post I get the sense that you are worrying a lot because of some relatively minor issues with a house you otherwise "love." Do you have a realtor? If so, talk to your realtor about this. If not, might be worth a few $$ to hire a real estate attorney to help you decide how to proceed with any of these issues.