The anti-seize turning into chalky paste is basically its way of saying it had a great time and hopes you never call again. Marine grease just quietly does its job like a boring coworker who never misses a day. Mine has been through two winters and the threads still look like they were cut last week. The galvanic worry is mostly a thing for fancy bike parts anyway, not your average steel crank. Cheap and slick beats expensive and gritty every time in my book.

I read somewhere that strong magnets can throw off a caliper's reading if it sits too close for too long, and the cheap ones are often the worst for it. Keeping the tray bolted to your cart away from your measuring tools should be fine, but I'd store the caliper in a drawer or case just to be safe. Better to spend ten seconds putting it away than trust a number that might be off.