I always turn off motion blur immediately in games that have an option for it. And recently I have started applying the same policy to TAA because it results in an effective motion blur effect as well.

I don't remember off the top of my head what my FOV for DRG is. I usually set it to 90 when I have the option to, but it's not always an option I can set.

Usually when I have issues with a game that cannot be resolved by setting changes, it is because of camera shake effects that I can't disable. I think in DRG's case, I was mostly able to disable the artificial camera shake, but there is a decent amount of natural camera shake from the engine/game physics. It's worse when there are modifiers that make me move faster. Those still trigger my motion sickness.

Also, something that's fairly unique to DRG is that it seems that complete darkness (like, where I can't see at all) can trigger my motion sickness as well. The vast majority of games don't have complete darkness in them, but it's a major element of DRG. I think that part of what made it bearable for me was getting decent enough at the lighting mechanics. Some mission modifiers that mess with the lighting still make me feel sick, though.