The Jul 15 date is for you to file. But since you will be getting a refund, it's not critical that you meet that deadline. There is no penalty for filing late if you do not owe.
There is no October deadline for filing a amended return (the Oct 15 date is for people who filed an extension, not an amendment; two different things). Technically he has three years (from when he filed) to file an amended return. But since he owes, interest and possibly penalties will mount up. So, he should file and pay as soon as possible.
