OK - here are answers to all your questions:
These were not weeklies, they were traditional 3rd Friday of the month options. I didn't try to close out the spread by selling the long call first - duh!!
Not sure why my limited posting history is an issue. I am 48 years old, and have been trading a long time. I usually just read the messages - perhaps I should have started off by saying I am a lurker, thank you all for all the information you have contributed that I have read through the years - and then explain my situation.
I am not an IB basher - I am a very happy customer. But this situation just does not make sense. On the phone, the IB rep walked me through my account, telling me which short option was paired off with which long option. My positions are all credit call vertical spreads on SPY. Exact same number of long and short. 120 in OCT and 60 in NOV. There are no other positions in my account.
When he said that there were 20 long NOV Calls covering 20 short OCT calls, I almost fell out of my chair! I repeatedly asked him why - he just said it is the automated margin process, and they can't change it. Even though it generated a clearly ridiculous result, which was 20 naked NOV Calls, with 20 long OCT calls not covering anything. Calculating the margin the correct way, which is clearly stated on the IB website as the difference in the strike prices, resulting in me only using about half of my equity - so I was nowhere near my limit.
Every spread was entered at roughly the same time, either through a spread order, or legging in. Usually 20 contracts at a time, either every day, or sometimes every other day. Remember, these were verticals, not calendar spreads.