There is another thread of users all having the issue of the poison spitters and worms dealing a massive amount of damage that you can't possibly survive once hit but Bob did not join the conversation. The change log from March 3 mentions an edit to the poison damage tick but as of today the damage is still insta-death. Is it a bug or is this how the mod is supposed to be?

Get better armor that has poison resistance. (I don't think any added by the base game resist poison, so your best bet is Titanium-Ceramic armor, power armor MK3, or better)

Since the poison spitters can only be found after exploring a fair distance, you're probably going too far too early.