Fold preflop as mentioned. On river, you probably want to bet/fold at microstakes and probably check at mid stakes, because at microstakes people will never bluffraise here (or raise with a hand that beats you) and at midstakes you probably want to check call (or check/fold depending on the player) because they're much more capable of bluffraising or going for very thin value here with, say, the second best straight.
As played, fold to the reraise makes most sense. I can't ever see this being a bluff, so if you're good, it wasn't a bluff they just made a random bet without any particular purpose. That sometimes happens at .01/.02 games.
This is also full ring, hence, the game should be interpreted as being nittier than short hand by default. I very, very rarely see a bluff raise river at FR plo.