Hi Barry
First off, stop setting yourself up to fail

.
You have so much in your favour - everyone has some problems, and yours are big, but as you say you have backup and support. So keep thinking positively, but remember that even if things don't turn out right straight away, you have the huge advantage over most of us here and that's youth

. If at first you don't succeed, try, try again.
Having said that, also take the advice to start slowly - you can't do everything at once, much better to start slowly, take your time to learn each stage properly, then move on a bit further if you want to. In practical terms that might mean to get a qualification in horticulture, then set up growing veggies on a scale where you can offer a box scheme. This means having a constant supply of veg year-round, and the ability to deliver to your customers, so requires skill and planning.
I don't have details of horticulture courses, but they're easy enough to google, then to get the opinions of others who have done those courses.
Once you have set yourself up as a market gardener successfully, then is the time to gradually add in laying hens, perhaps a pig or two bought in as weaners each year and raised to slaughter weight on a spare piece of land. Perhaps add a goat or two for milk and the occasional kid for meat. From then you will know if you really want to go into it big scale or that you are happy as you are.
You will know by then how the new pills are working and whether or not you can guarantee that you will stay out of hospital. A horticultural enterprise can manage for short periods without supervision, but animals cannot, as you know, so realistically you would need to know you had a reliable stand-in to take over their care if you did have to go into hospital at any point. Of course everyone is at that risk too, but you would be sensible to work out a worst case scenario, and make provisions for that in advance.
Again being realistic, agriculture is one of the industries with the highest incidence of depression and other mental illnesses in people who did not suffer from them at the start of their careers. It can be lonely and stressful.
If you truly want to go into full-on animal husbandry, then what you need first is
experience. Even if you choose to take an agriculture degree, and Edinburgh Uni does one of those, then before you could even be accepted onto that course, you would have to show that you have plenty of
experience. You would be up against people who are in line to inherit the family farm, and who have a lifetime's experience of what's involved, plus the advantage of not having to buy the farm in the first place. It's possible, but very, very hard.
Sally's mention of WOOFing is a good one. This started off as 'Working Weekends on Organic Farms', but has morphed into more than that now, so you can spend much longer times on one farm, usually a smallholding, and really learn what's involved, both in the care of everything they have, but also in just how heavy and continuous the work is. You can do it, but you need to know in advance the totality of what is involved. Of course on top of the actual outdoor work, many people working on the land also have to spend many hours doing the books, filling in forms and obeying the great master of the Government.
Another possibility someone mentioned on your first post was volunteering at Gorgie city farm. Once it re-opens to the public, go along and have a look and see if you think that might help.
Did you ever get those windowsill plants to at least start growing something this year?
Every little thing is gradually building up your knowledge and experience, successes as well as failures. In fact possibly we learn more from our failures than from our successes.
There are loads of books around, both instructional and histories of the actual experiences people have had in setting up various horticultural and agricultural enterprises.
Get reading, get some practical experience and the very best of luck