wish i could help but i've been unemployed for 2+ years. i have amazon cred, but i just realized recently that you can't buy amazon cred of any kind with amazon credit (to trade, give away, etc). it takes it off of your card you have on file. i went through with a transaction just to see.
on other things like instant codes for msp, you have to do the 1 click and enter, or verify, credit card info. once it goes through though, it will take the amount out of your credit 1st (not gaming promo cred, but regular amazon cred). not so with gift cards, and it does say so in the fine print, but i could have sworn i'd have bought egift cards for people (probably a year ago) that took from my amazon cred. oh well.
still best of luck, pal. one more bump for you!