Avoid Poi Pet if you are not familiar with border runs, it's a shitty border. Laos is very easy, either Nong Khai or Mukdahan border. You don't need anything, just your passport, and some money. Not sure post-Covid, this may have changed.
You can do everything on your own. It's the simple answer, there is nothing else to add to that. It's not 100% success rate. Here in Chaiyaphum, you can do whatever, it's a chill immigration.
You are asking too many questions. You are asking agents to share their secrets. Everyone takes their cut, it is bribery. It's not legal per se but it's legit. I've used Thai Visa Centre many times in the past. They are legit. Understand that you are paying more to have peace of mind in the process. The way things work in Thailand is not something you can understand after being here only a few months. So you will have to accept not knowing everything.
You are obviously a rookie, so I suggest you humble up a bit and listen to people who have been here for a very long time, like myself, Alan and Stuart. If we tell you that the wording is correct, it's because it is. Not understanding the wording simply mean that you are unfamiliar with the jargon. Everything Alan said is 100% factually correct. Again, you are simply not custom to such jargon. Be willing to learn instead of arguing non-stop.
Brah, it happen to me before. You must be awful at talking to people. Grab any janitor, bring him to the ATM and mimic what happened to your card. There is a number you have to call and they will come retrieve your card.
You paid a bribe as insurance. Not saying that it's fake but the amount of profit they make out of this insurance is insane. You are not supposed to open a bank account with nothing but a passport. Usually, your rental contract is enough.