We'll have to work on one thing at a time. I think the error in your add to cart button might require you to delete your winfilecache .dat file. You can search the forums on information on how to that.
You will need to remove the dollar sign from the database or strip it out in the query or in php. You need to pass a number without currency symbol to the price field.
Continue shopping should work, but it might have a problem due to the other add to cart issues. Get add to cart working first before worrying about continue shopping.
Did this help? Tips are appreciated...
