For me, I tend to withdraw 50% every month. I make enough from FX to live on but, in saying that, it's not my only source of income so I don't really stress over how much to withdraw - sometimes I don't withdraw anything. Over the years I owned and sold a few businesses and now own one that's somewhat automated + have other investments such as property, so that's where the bulk of my equity has come from. FX more just pays for vacations and things like the $5,000 mountain bike that I've only used once.
If I were to do it full-time as I'm sure I will one day, I'd simply put more money in the account and increase the position size respectively, taking out 70-100% of profits each month.
I used to manage money for a handful of wealthy family and friends and we used to compound the account, only withdrawing every 10-12 months. We were making some great returns and, by not withdrawing anything for a year, we saw the account grow very quickly. We made over 125% in under two years. We averaged around 6% per month with some huge winning months and some small losing months.
As for your questions/comments concerning EA's, I'm really not the guy to ask. Rick and Sharks would be more help than me.