20% monthly limit will not give you 5 months. the nominal 20% of the capital will. You can even risk 50% and stay in the game for months..
1000 (risk 500)
500 (risk 250)
250 (risk 125)
125 (risk 62.5)
62.5 (risk ...) and so on.
drawdown is just that.. you lose 50%, you lost 50%. you reevaluate just like new levels, as you are now given new numbers to work with.