MBP will not boot off of USB Flash Drive

Yes, that is it for your graphic card, symptoms described are typical of its failure. There’s a number of workarounds out there for the issue, harware, software and hybrid, just google for “disabling graphic card on 2011 MBP” and you’ll be taken to the most populare solutions, you’ll have just to choose for the one that suits you best. However, since you mentioned Photoshop, your needs in terms of graphic resources may not be satisfied by the now a bit outdated Intel HD3000 shared card. If that’s the case, you may look for a replacement 2012 logic board which is a bit more reliable or go for a new Mac. I would avoid alltogether “reflows” and “reballs” offered by some labs, usually just a waste of money.