Blackhawk

So I'm looking at about a $40K signing bonus.

1. Looking at deferring class from mid December 2017 to mid January 2018 for tax purposes as that would put us in the top tax bracket for 2017 (wife works as well). Thoughts?
2. Signing bonus comes with a two-year prorated contract. My intent is to just invest the signing bonus and sit on it. If I make it to a major prior to the two years, give back what I owe. If I do need to pay back part of the signing bonus, how do I figure that for taxes? File an amended return?

Thanks.