It sounds like you would feel more relaxed with something that could give you confidence,but you own something that needs to take confidence from you?? Common problem and although I can say from experience it does get better,the ups and downs in the meantime can be quite dis-heartening.
I think you are wise to be thinking very carefully about sharing a horse that can be difficult on the ground.Could be opening yourself up to a whole world of trouble if you get the wrong person.
I have a saint to ride but rude on the ground welsh cob that I am advertsing for share and I have said in his ad that he can be a right git on the ground and made him sound worse than he is TBH,but I would rather do that than have the wrong person and he drags them off and injures them because they weren't confident or experienced enough to handle him.
I also intend to be there with them every time until I am happy they can manage him on the ground.
My saving grace is that my lad is bombproof to ride,so it is only the ground issues that I have to be selective about.I agree you are going to find it difficult to find someone for a difficult horse on the ground and that is green to ride like your lad.You are certainly going to find it difficult to ask much money for a share as really they would be helping you with his education and manners as much as you are helping them by providing the horse.
I had a sharer for my youngster who was shall we say 'not easy' (understatement lol),and worked great,but she was a over brave teenager who had no problem wth the ridden side,and my lad has manners to burn on the ground (took many months of work but we got there) so that wasn't an issue.There was no money involved as I looked at it that she was helping me out with his ridden work so was working both ways.
The point of my long winded waffle lol,is that it *is* possible to find help for not so easy horses but you may have to be prepared to wait for the right person and be flexible on issues like financial contribution.You may also have to hang around with them the first few weeks or even months until you are happy they can manage the horse safely.
It sounds like ultimately you need a different type of horse TBH,but if that isn't an option anway then you may as well stick with what you have and try and make the best of it (or sell,but I'm guessing that not an option you want to try just yet??).
Put up an ad but just be careful how you word it,and don't be afraid to be honest about what you are looking for and what the horse needs.More than perosn has said to me about my ad that what they liked about it was the amount of detail (yes I waffle on ads as well:tongue
,and the honesty,made them feel like they knew exactly what to expect.
You may not have loads of replies as I didn't for youngster (I did for cob but that's because he's a 15hh bombproof and safe cob to ride,what everyone wants it seems),but what replies you do get will hopefully be serious enquiries and suitable for your horse.