if you get a retirement visa you can not be employed in Thailand I think a lot of people misunderstood as you had 2 different questions in one 😉 hopefully all works out for you
Basically I would tell the agent and wife you have no money left leave it for a month and then see where you are at you will know in your own mind then
Does your wife have a job or own land etc in Thailand the visitors visa will look for something for her to return to Thailand you need evidence of your relationship etc .. and second I don't think £3000 is enough to retire in Thailand I think you need to open your eyes and stop living in a dream world