A couple of things that bother me about how you report. You have stated repeatedly that these credit spreads are a minority allocation to your portfolio, something on the order of 20%. I may be wrong, so feel free to post the actual percentage. If so, it would be impossible to earn 16% on portfolio, as it would imply earning an average of 80% on each position, if calculating return on risk on 20% of your total portfolio.
Obviously these positions are not earning 80% on risk, they're averaging 16%, and therefore you're calculating your return on $ at risk, not the return on a minority portfolio allocation. In and of itself that's no problem, as long as it's understood that the entire account is at risk (less the credit received). In this case, risking upwards of 90% of the account.
In March you posted a >21% loss. There is no way that you covered the average NDX vertical at a 21% loss. It's obvious that you're calculating your profits on risk capital and your losses on a "diluted" portfolio. If I am wrong that please correct me. If so, you are misrepresenting your performance. No legitimate manager reports performance in such a manner.
Also, how is it possible to "run out of cash" to close positions when there is no variation margin involved in a debit spread? The net liq on the account would have no impact on your ability to cover a vertical spread unless all spreads blew-out and you would lose more to cover than would be lost holding to expiration. IOW, the possibility of going debit due to microstructure (10.00-wide spread offered at 10.50).
You have no credibility if you are reporting winners as return on "dollars at risk per position" and losers on a diluted portfolio. You are, without question, calculating your winners on "dollars at risk", and I suspect not reporting losses in the same manner. HUGE problem.