Only #2 and #5 are correct on your list. There's NO jet lag between Thailand and the UK! Plenty of authentic Thai food, especially in London. You can easily install a 'bum gun' if needed. The clothes will go to good use in Thailand (it does actually get cold there)
It can take at least 6 months after your child is born to obtain custody rights because you need to go through the Courts. Your best bet is using a 'border run' agency.
Not strange at all. Been stopped at road blocks a few times, never been asked for an IDP only a driving license. It's not actually a requirement to have one.