How do I get away from a hand?

I run in to this problem all the time playing micro stakes SnG's. I play very very tight and aggressive. I only play premium hands in position and I play them very aggressively to isolate. However, I seem to run into problems with this and can't get away from it. For instance I will get JJ or AK in middle position, everyone before me has folded, I will raise 3x to isolate and a loose aggressive short-stacked player will shove over top of me. I feel obligated to call every time because I know the guys range is really fishy, he's already played way too many bad hands and is tilted and shoving random cards. I end up coin flipping my JJ vs A3o or my AK vs Q7. Am I correct to call these shoves even though I seem to lose very often?
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A second problem I run into often is that I will be in late position with a premium hand with a lot of limpers behind me. I'm unsure of how much I should raise to isolate. I've heard 3x + 1 for each limper. However, I find that in these micro stakes, once a player has limped they are committed to seeing a flop regardless of how much you raise. I will often have 5 people limping in for 50 chips and I'll raise huge and still get 4 callers. Maybe I should just shove all in preflop if I have a premium hand against a table of limpers?