How do you fix Wally West?

[Potanical Pardon]

I wasn't aware of that. Welp, Boomers, amirite? j/k

[married guy]

He doesn't need fixing.
Simply ignore all the ridiculous crap and concentrate on writing great Wally West/Flash stories again.
Set him back into Keystone, Linda, kids and go nuts.
He has strong links with the entire DCU. From JLA to Titans to the Rogues. You could write 2 years worth of stories without scratching the surface.

[Waterfall]

Retire him. He offers nothing to franchise at this point. Speed Metal wrapped up the problems with the character. Now he's ready to bow out from superhero game and settle down with his family.

[Dataweaver]

For what it's worth, what I've heard it's that the plans for 5G involved bringing everyone's stories to a close, followed by either a time skip or just the imposition of the new timeline with age adjustments and the introduction of the 5G replacements. While the “payoff” has largely been scrapped (if 5G happens, it will be presented as an “in the future” event), the lead up that involves wrapping everything up still seems to be in play.

So with that in mind, I won't be surprised if Wally does retire after Death Metal. But if he does, he's unlikely to be alone: expect Barry to retire as well.

[Godlike13]

You move on to something else with him.

[Frontier]

Give him a book.