I think you are probably right to overwinter him this year, so let me know what you think of the suggestions in that article. You can get extra light into the table by using something like one of those bendy desk lamps that is bent so that the light focuses down into the table. If your temperature is correct (and do please measure it at various times of the day), then you don't want more heat -- just more light. You could try takng him out of his sleeping or hiding place several times a day and put him under the lamp. My tortoises usually try to go into hibernation much earlier than I want them to, so I put them under the lamp several times a day. For the first few weeks they head straight back to their sleeping area but after about three weeks they seem to give up and wake up, so be persistent.
Do grow the seeds. It's a good idea to grow the seeds in succession in a series of small trays, so that when the tortoise has eaten everything in one tray the next tray is ready to go in.
I don't think you need to bathe him for that long -- 15 - 20 minutes should be fine, but do make sure that the water stays warm, so either do it under his lamp or if you put the bath somewhere else then just take some water out and add some more warm water as needed.
The only commercial food that we would recommend is Testudo Pre Alpin. It is made completely of alpine flowers and meadow grasses and is a really good food that his not too high in protein (like some commercial foods). You can buy it from the Torts in Need selling page here: https://www.facebook.com/groups/1081663048534074/
, and they also sell other good products and seeds. You can also buy small bags from places like the Shelled Warriors shop https://www.shelledwarriorsshop.co.uk/a ... -261-c.asp
and I would get the smallest size they offer as it lasts a very long time (you went the dried mixture and it expands enormously, so you only need a tiny bit at each feeding. He might not take to it at first, but if you mix it with wet lettuce leaves that have been cut up into tiny pieces, so that the new food sticks to the lettuce, he will gradually get used to it. I wouldn't buy any other commercial food -- just Testudo Pre Alpin, although you can buy individual bags of dried weeds from the sites above and they should be fine.
Another tortoise isn't a great idea at the moment, because you won't know what sex your tortoise is (he is almost certainly too small to sex) and if you happen to end up with a male and a female they you will have to separate them because male tortoises make life miserable for females. In the wild they tend to be pretty solitary creatures, although two females can get on very well.
More entertainment is a very good thing, as tortoises get bored if they can see from one end of their table to the other end without interruption. So putting in things that they have to climb over or walk around is always a good idea -- rocks, plants in pots, like spider plants or ornamental grasses, those bendy log things (I think they're called 'fiddle sticks' that you can buy in pet shops -- tortoises love to climb up and over them, or hide inside them. All of that helps. It looked like you've made a hill of substrate in the middle of your table, and that is great -- really nice for him to walk over/around and dig into!
Have just seen your post about the thermometer. Yes something like that is perfect, but you could do even better. I can't see how much yours cost, but the best ones look pretty much like that (a digital display unit and then a probe on the end of a cord that you can hang down into the table to register the temp under the lamp, but you can get ones that have a Max/Min function (where you can see how hot or cold it got since you last re-set the function. Something like this (but you can get them in lots of places)
https://www.pharmacy-equipment.co.uk/di ... ter-tmm105
Oh dear, I've rambled on far too long! I hope that some of this helps or gives you some ideas. I think you're doing a great job with your little one (what is his/her name by the way?).