problem with short-handed aggressiveness

[Navers]

The other day I played a friendly short-handed home game with three other people. It was a NL game with 5/10 blinds (that's cents, not dollars). My aggressiveness was paying off in the beginning, but as the game progressed I started losing large amounts of money as they started calling my big raises with mediocre cards.
.....For example, I thought UTG was trying to steal, and with A9suited I raised the pot to $1.50 because this was shorthanded and the game was rather loose. I didn't want a cheap flop for anyone and I wanted to cut down their implied odds. They both cold called and the A2o (UTG+1) won with a straight on the flop. , I bet out 50c on the flop and a dollar on the turn since there was a flush draw showing on the board. UTG+1 won by just calling my bets.
.....How should I have played that hand? I think now that my preflop bet was too big and risky, but how can I drive out players? Should I have driven them out with that hand?How much should I have bet to protect my hand and expect a profit with less variance? Also, how tight/loose or passive/aggressive should I be in these loose shorthanded games? Should I wait for premium hands since the postflop bets are significantly larger compared to the blinds and be assured a win? Or should I play medium suited connectors? Any help at all would be appreciated.