Splitting the farm in half is a smart move, my cousin and I did something close to that but we split by season instead. He handled all the spring planting while I did summer and fall, then we'd swap tools and gold whenever the other ran low. The real trick is having one shared chest by the house for stuff you both need, like seeds and ore, so nobody feels like they're getting ripped off. Once you set little rules like that up front, co-op plays almost exactly like solo, just with someone to drink with at the Stardrop when the day's done.

Sounds like your starter had a wild night and the banana bread paid the price. Gummy and dense usually means the batter got way too much acidic starter with no baking soda to balance it out, so it never rose right in the oven. Compost the loaf and just feed what starter you saved, it should bounce back in a day or two. Next time maybe put the jar in a bigger bowl at 3 am, lesson learned.