I think that this is an easy fold as any 3 bet on a UTG raise is showing serious strength, even if it is from a short stack. Too likely for him to either have a pair TT+ or overcards to your 99 which only makes you a 50/50 chance of winning the pot. Also remember that he is 3-betting you from UTG+1, not from late position, so it shows even more strength from him. I find that a lot of times in these low stakes cash games people buy-in for the minimum specifically so they can profit from hands like these.

Seems too light.

I felt like it was but wasn't sure which pair I should start stacking off here with.  I guess JJ+ maybe or if villain is super tight then probably QQ+

it does seem light and is an easy fold with no history. against some players who will call with small pairs it might be close but as standard I think you need to find a fold in this spot.

I think when you playing against SS'ers and don't have any reads - assign them a initial 3b range and see how your pair does against that range. For future posts you could consider leaving out the results as the analysis tend to get somewhat colored by it :)

I work with a basis assumption that SS'ers 3b most pairs +77 and AQ+. Against that range we are 45/55 ish. When you jam you will only get called by the top part of his range that has us crushed. I don't like calling in this spot as playing OOP on a board that we will often miss and have little eqt on most boards which really sucks. We cannot profitably setmine either because he is short stacked.

On a side note we tend to make good money on the (bad) short stackers when calling them in SRPs as they tend to play really bad post flop. They often fire once and give up because:

1. They live for playing fast preflop and don't know post flop play
2. Bad at reading board textures
3. They don't have leverage post flop with their short stacks 

Calling them IP can be a gold mine :)

Hope it makes sence - first post here on RIO