I would strongly advise that you install a front brake (if you haven't already) because you're new to fixed gear. When you become more comfortable with riding fixed, you can make your own decision as to whether or not you need/want a brake.

Getting used to foot retention just takes time. Are you using the stock pedals? They absolutely suck and are a pain in the put to get into.

Sometime it takes people a week or two to get used to fixed gear riding, sometimes it only takes people a couple of minutes. On the flip side, after riding fixed every day for about a year now it's really weird for me to ride a bike that can coast.