@Onetwothree45 When I mentioned being creative and money, what I meant was my actual livelihood depends on me having a large variety of materials on hand to create from. Not hobby buying and selling.
I do also however hoard items for DIY projects and yes it often takes a long time to achieve them. This is what sheds are for - to house things that are going to be used for upgrading home and garden but would be in the way of normal living in the meantime.
You mention his mother bulk buying. This can be about using money wisely, thus being able to afford things, but it also suggests he's probably been brought up with the 'it's a bargain' mentality.
I've been a member of both camps, and still bulk buy things I use a lot of regularly, or where I'm sharing it out with others. Bargains are anything from a sensible opportunity ie a discounted air fryer replacing oven use, to a simple dopamine hit- buying something you had no previous need for because it's available cheap.
I'm also well liked, not a recluse, and help others a lot. If you met me I doubt you'd peg me as having a MH condition. Most of us aren't Mr Trebus, and those who end up on TV programs. The condition isn't chosen, and for me it was simpler to let go of life, than to just get rid of everything. He can't just bin it all for you. There are a lot of things he can do, but right now you need his stuff out and to stop chucking, charity shopping it, and making him throw it away if you don't want to entrench him in compulsive hoarding deeper, because that's what you are doing.
I will say again learn properly about hoarding, But also learn about Co-parenting, because what you're currently doing to him trying to mold him to fit, is going to destroy your relationship anyway, outside of what him doing, will.