Get a folder and keep multiple copies of all your documents in there together with a few passport size photos. You can then take your passport and the folder with you to immigration every time you attend and you should have everything you need.
I think it is cheaper if you change it into Baht before sending it to your Thai bank account. I'm not an expert, someone will correct me of that's not true.
It might be easier if you explained the type of things you want to do in your retirement. Everyone is different and will have different hobbies and interests and the people that reply to you are likely to be different to you. Me personally, I love the outdoors and walking on the beach, I also have a house and I am renovating it. I love the people, culture, climate and beaches. I used to play sports, but injuries restrict that now. Thailand is very safe as others have said.
This is ridiculous, you should not have a problem opening a bank account with a non O visa. Whereabouts are you? Perhaps someone knows a compliant bank where you are. Avoid the banks in shopping malls, Bangkok bank is usually the easiest. Dress smart, be polite, and take a Thai speaking person with you.
that's true, yes you need to wait a few weeks, but you don't need to do anything other than go back to the office to collect it. As for the paperwork, I just have a folder with several photocopies of each document inside, so I simply give them the required number of each document. I guess some people might find these things challenging, but if you are organised I think it is very easy.
The process should be quite straightforward for your husband, he will have the long term visa and can therefore open a bank account before extending his stay. Your situation is a bit more complicated, but maybe a bank will be sympathetic and open an account for you at the same time as your husband. If not, you might need to see if an agent can help you with that part of the process. Everything else should be fairly straightforward, as others have said extend your tourist visa and then apply for the non-O. If all else fails, you might need to go to a neighbouring country like Vietnam to apply for your non-O, before opening your bank account etc. Good luck.