Summers where I live typically have 80F nights and it can easily pick up to 95 degrees during the day.

I have a plastic trash can (which I bought for this purpose) that I have filled up with water. Currently, my apartment measures 79F, but measuring the water in the trashcan gives me 70F. 

1) Can I just place my fermentation tank in this tub of water to counter the heat? An employee at a local brew shop said no, the temperature of the water will just be room temperature. However, it is currently reading 9F below room temperature...

2)Will this method work during the summer, when I have a 90-95F day?

3) Will bacteria that collects in the bucket of water be a greater threat to my vodka-filled airlock than the bacteria that collects in my closet, where my fermentation tank is currently stored?

Thank you!