1/2" is way to thick for most parts of the suit. As stated, Big Lots carries the 1/4" foam in rolls for $16. I'm about to start on my third roll. I got two helmets, both full arms, chest, back, abs, cod and one thigh out of two rolls.
When you cut off pieces from the roll use a heat gun on the front and back to flatten it out. this also makes it a little firmer since it melts the foam a little and then hardens up as it cools. Once you cut the pattern use the gun again to re-heat the foam and shape it. One thing that I found helps is after shaping the piece I throw it into my mini fridge (which is right next to my desk) to cool it down faster and harden it up a bit.
I'm new to the EVA process as well but I have learned a lot through trial and error as well as answers given on RPF.