You don't need to clear the texture cache unless you're using texture compression (which can delay--but not fix crashing). Mipmaps being off may help delay your crashing also, yes. Remako is fine to use (it's not using insanely high resolution upscales).
The current version of the game (Aali) driver is simply poor at memory management (so was the original Aali driver, it's just more pronounced now). The best thing you can do is save often and if you crash, restart the game. You could go 30 minutes or 7 hours, it depends on so many variables. We're investigating the issue and hope to improve the stability in the next 7H 2.0 update.