My wife and I recently moved to Germany. She's a Swedish citizen, and I'm American. It'll be December before I can actually apply for my residence card, because my appointment to register our address is so far out - the local police station was all booked out and we didn't get an apartment right away.

I imagine that I won't be getting my residence card until well after Christmas, by which time my 90/180 days will be passed. What if I want to leave to, say, London for the holidays? Will I be allowed back in? I hit day 90 around the 21st of December. I could maybe leave on day 89 and come back on day 90 (with my wife and our marriage cert), or use this Polish solution: https://travel.stackexchange.com/questions/7154/us-citizen-in-poland-more-than-90-days-in-a-180-day-period, since I can't be expelled from Germany for overstaying my visa while my application is processing.

Both of those seem a bit risky though. Am I reading too far into it, or is this a legitimate concern? Will I get some sort of documentation saying I have a residence card application processing?