Yangon does not accept payment through the e-visa system. Same as both consulates in Laos. Payment must be made in person at the embassy but at Yangon you're required to have an appointment to pay.
you cannot use it in Thailand. You can only use it when entering. And if the embassy finds you went to Thailand they will cancel your application as you're required to remain inside the jurisdiction of the embassy during the entire application process.
What does your lease say? Generally you either get the bill directly from the electric company and pay the government rate, or you pay a rate that's 2-6x the government rate as a way for the owner to make extra money off of you. Either way it should be in the lease.
yes, definitely. The LTR application doesn't care where you are since the BOI does the processing. And if you're already in Thailand you can pay the exact 50,000 baht to immigration rather than the inflated embassy price. And even better, you'll get a big stamp in your passport rather than having to carry around a printed visa for 10 years.