Hi :) 30g is probably too much, and I feel like the more you take, the more likely you'll vomit, even with anti-emetics.
From 8chan: "Wikipedia reports (with dead link to an older source) a lowest lethal dose of 71 mg/kg. So, if your bodyweight is 65 kg, then the lowest lethal dose would be 71 mg/kg * 65 kg = 4615 mg = 4.615 g. Calculate this with your weight and multiply it by 3, just to make sure."
I've checked that wikipedia source and found a cached copy:
https://web.archive.org/web/20110309012317/http://msds.chem.ox.ac.uk/SO/sodium_nitrite.html
I weigh exactly the same as you, so 71mg/kg * 110kg = 7810mg = 7.8 grams. I plan on taking 20. All that said, there have been cases reported of people dying from as low as a 2.6mg dose. People have died from accidentally putting nitrite instead of table salt on their food. 20g itself is probably overkill, let alone 30.
The PPH says that the typical timeline is at 5 minutes after taking it, drowsiness, at 12 minutes is usually loss of consciousness, and at 40 minutes, death. SN is somewhat a new-ish choice especially for Exit, so they have less data on it and might well be wrong. There's been posters on here who have stayed conscious for 20-30 minutes, and if I recall correctly, someone who was found at around an hour and was "rescued"/resuscitated. Give yourself as much time as possible, overnight would most likely do it. Good luck with whatever choices you make x