Your history sounds fine. Especially that you had actual visas and not a bunch of back to back visa exempt stamps. You mentioned 7-8 months, which is impossible, was it an METV visa where you left every 60-90 days?
All entry stamps will be 180 days, that's the length of admittance per entry or extension, your email PDF approval states the validity/expiry of the visa.
Pick one category, medical route looks legitimate according to your age. Check posts for successful approvals in your chosen category at the embassy you're considering to get an idea of what they find acceptable. Get a letterhead document from the clinic outlining your diagnoses, treatment plan and follow-up with appointments set up.
You get the satisfaction of taking and looking at the pictures of you and the wife in the bedroom, living room, in front of the house number for immigration office purposes.
Anonymous participant he applies as spouse or dependant, references your approved DTV visa number, provide 500K+ bank statement, marriage certificate, ID for both of you passport photos etc.
I don't know why they would want to see your visa, passport data page yes. Been a few years since I've renewed, so can't say I'm in the loop currently in that regard.