Grew up at DL, first time at WDW!

18 days until our first trip! I have a few specific questions that I couldn't find answers to by reading through this sub. I grew up going to Disneyland every summer and it was fantastic. My memories are nothing but pleasant. Since moving east and having a kid I was hesitant to jump on the WDW train but since we will be near Orlando for a wedding anyway we figured what the heck! We are booked one night at AK and 3 nights at CBR. Our son is turning 4 while we are there so since he is still little we are keeping it relaxed with two not-so-jam-packed days at MK. We scored a lunch res at BOG for one day so hoping it's cool. Grabbed a few other ADRs as well. FastPasses are also booked. My questions:

1. for the love of god please tell me that MK has churros! I've seen conflicting information on this.
2. anything I will miss from DL that MK just doesn't have or do as well? DL manages to feel intimate and I hope MK is the same way.
3. is using Uber instead of the buses a good option? Obviously Uber isn't free but we don't have much time & don't want to spend hours getting around and would rather shell out extra to avoid waiting. Will Uber drop us close to MK entrance?
4. how close to an ADR can you cancel without being charged? And what is the charge if you miss the cutoff?
5. if you have a FP at a certain time but see the line is short enough to wait can you just modify that FP for another ride?
6. is the pizza delivery service at CBR reliable? Tasty? Since a lot of the areas are under construction we won't be spending much time there but might order in one night... assuming it's edible haha.

Sorry for the super specifics questions that only pertain to my trip - but hoping other's can gain from this knowledge as well. Thanks in advance for sharing your wisdom :)