Wow you've tried the whole industry. The only thing I can recommend to you would be to try a brand of drops called Optase, they are more quality and thicker than everything else on the market.

Here's a HN post with a really good top comment that talks about psychological eye strain that really resonated with me, plenty of other advice in there too you might like: https://news.ycombinator.com/item?id=34518343

Good luck!