Solvent-based gloss still giving off nasty fumes after month and half. Tried everything!

I'd start again and use a water based gloss I'd sand the solvent based gloss underfoot and apply a water based gloss

Forget solvent/oil completely if you are getting migraines. Lightly sand the woodwork. Get a good quality trade primer/undercoat such as Zinsser Bullseye123 or Bedec aqua undercoat. That should help to 'lock in' the nasty chemicals. Then use a good top coat, again Bedec aqua satin and gloss is really good but you could use crown or dulux - just make sure it's water based and not oil. With modern paint technology there is hardly any need to use an oil based paint except for solving rare problems. Water based trade paints are as durable as oil once they dry properly and contain less harmful chemicals. So don't let anyone tell you oil paints are better - that is no longer true.

If it is dry, lightly sand, clean down & oil based undercoat it. Then once dry same perpetion but use Aqua undercoat. Then use whatever you want over t hat. Good luck

I would sand down apply water based undercoat then water based gloss