Well, he did state his brain draws great amounts of energy from his body, hence the ALS, and the chair likely provides life support energy for him.
It is possible that the only "cure" for him is to revert his brain to how it used to be.
As to why he is attacking Barry.....unless I missed some pivotal dialogue, which is possible given my overall feelings of late, I do not know why he is doing this.
He has the intellect to basically solve Earth's assorted problems, clean energy, "climate change", terrorism, etc. Yet he isn't doing that.
Maybe the Thinker wants the Flash's body. That way, he has all the energy his mind could possibly need.
It's interesting that a hero/villain performs one amazing feat, or use a power they haven't used for 20+ years, and that automatically propels them to a high status despite scans and evidence to the contrary. I don't know what is worse, selective feat picking that has only been done once or twice 20, or more, years ago or ignoring evidence from scans or the lack thereof. We need to stop putting our favorite heroes/villains on pedestals and start putting them where they really belong. But it's evident that people never will because they would rather accuse others of cherry picking feats, when they don't, and being 'morally superior' when they aren't. I guess being honest and as fair as possible only opens one up to being the target of childish accusations and fault finding by those who insist on acting petty and childish. What happened to a good debate between two civil, mature, adults?