The chipstacks are completely meaningless if not in relation to the blinds. If you have a couple of short stacks I would just wait for a good hand because they have to shove at some point and you should only call if you're confident that you're ahead of their range. If you for whatever reason raise QJ from MP and a shortstack comes over the top you might even have to call and probably double him up. So this is not a good idea. Keep playing reasonable hands... especially in 30$ and less buy-in tournaments. No point in getting tricky, just bet when you have it and fold if you don't basically.

Never ever push SC's!!
They are only valuable in a multi-way pot when most of the players are relatively deep. There is no way you aren't dominated if you get called.
The only time I push SC's is in situations where I would push any two - for excample as a 5M shortstack on the button if everyone else has folded.
A3 is a better hand to push than 45s if you have to.