I mean I consume maybe 6-7 mg of nicotine, but probably less, per day by vaping. At 0.8mg/kg I would have to consume over 80 to reach LD50 and I believe that has to be in your blood at once.

My caffeine intake is around 400 mg per day. LD50 is over 20 literal grams.

Going by these numbers it does indeed sound like the nicotine is worse, but neither one is ever going to get close to the LD50. If I were to significantly increase my nicotine intake, it'd get nauseating for me pretty fast. Caffeine I could probably double without noticing a damn thing, but beyond that I think it will start affecting me too much too.

Also that's over a day, whereas I believe LD50 implies it'd have to be in your blood all at once?

The LD50 is meaningless if you don't have the standard dose for comparison.

Also, the LD50 of ingested nicotine is closer to 6.5-13mg/ml, or the equivalent of over 130 cigarettes.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3880486/