It sounds to me like you have a good set-up (so that is a great relief, as many people are badly advised when they first get a tortoise). 35C is a little too hot, but because he can wander away from it then he does have the freedom to regulate his temperature, which is important. Can you possibly raise the lamp a bit higher above the table? That would result in lowering the temperature a bit, which would be better. Is this a combined heat and UVB lamp, or do you have a separate source for UVB (like a UVB fluorescent tube)?
It sounds like you are giving him the best selection of food that you can at this time of year. Re the food he doesn't like (kale, rose petals, etc.), sometimes if you try rubbing a bit of cucumber on the food that will entice them to eat. Most tortoises love cucumber (do peel it though), and although it doesn't have a lot of nourishment in it, it does contain a lot of water, which helps to keep them hydrated. Also, given that it is so hot under his lamp, it is important that he is well hydrated, so do bathe him daily for 15 to 20 minutes, in a container that he can't see out of, in warm water that comes just up to his chin (or where the top shell meets the bottom shell). He might or might not drink, but it will help to keep him hydrated, plus they usually wee and poo in the bath, which means less spot cleaning in his table.
This link might or might not help. It is to our article on introducing a healthier diet. You are already offering him a healthy diet (and I hope you are also sprinkling a good calcium source on his food -- like Nutrobal - as that is very important for a young tortoise), but he just isn't eating, so some -- but not all -- of the principles in the article will apply to you. It might be of some use:
https://www.thetortoisetable.org.uk/tor ... FgWx83gq9s
Is it possible to send us a photo of his set-up? As I said at the beginning, it does sound very good to me, but sometimes with a photo you notice small things that can make a difference.
Just one other question -- did you buy him from a breeder or from a pet shop? Sometimes tortoises from pet shops can have a worm infestation. This isn't serious and can be easily got rid of, but it can result in lack of appetite.
Cheers,
Nina