Get a visa first in UK and even that don't guarantee entry, immigration can still turn you back if they see fit.

What can possibly go wrong....

Don't need to be married at all

7-11

Friends, relative address. Keep a UK mailing address and all good

LTR is the way forward as long as you really meet the criteria and will again in 5 years . It's fairly simple and does what it says....I got mine 2 months ago

It says on the visa itself -60 days , then if you want to stay longer need to get an extension from Immigration, do a border run or fly in/out again

Sounds dubious to me. I applied several times for my partner, not even wife, and always do it direct with Embassy & VFS do the interview and she goes alone And never been asked for 62k deposit proof, although my bank statements are included . May be too late but look at doing it direct....as long as wife can speak English at VFS, and evidences a reason to return to Thailand you have full control

FATCA rules for reporting US citizen having bank account here

Not a hope as it is, never get it legalised. Bring it in bits and reassemble and have it on your own land is about as good as you get, and even then chances of getting it in , all of it, without being checked are poor.