What are the visa options for expats looking to marry and apply for retirement and spouse visas in Thailand?

Hello, apologies for such a long story but I was told I would get best advice from here.

My partner and I are having a nightmare with visas. To cut a long story short, we moved here in April with the intention of getting a retirement visa for myself but my partner , Sean (we’re not married, both from UK) aiming to get a business visa and work permit via our company. Without going through details, this is now not an option for him. We are both on a 30 day extension. After some problems with our agent, I was late in applying for my 90 day non O (i have all relevant documents and money) and consequently we have to do a visa run next week. We have been told, aside from Sean getting employment with a company, his best visa options are either ED visa or a spouse visa (?) where Sean can tag onto my retirement visa. Obviously we have to get married for this (another hurdle, but is doable).

My questions are a) how long will it take to get married in thailand - will we have enough time for the applications for 90 day non O and his spouse visa? b) do we apply for both at the same time? C)if he opts for the ED visa, does he have to stay on that visa for the full year if he is lucky enough to obtain a job with a company in the year? And D) are there any other visa options (he is 54, no pension) Thanks in advance for any advice.