AEs are not necessary per se but they increase greatly your chances of success as they help you keep the SN down and speed up gastric emptying and so absorption.
Painkillers, as the name suggests, helps with the pain and discomfort you might get from the headache.
Benzos help with the anxiety.
Other meds are not recommended. There are debates about the usefulness of antacids, and betablockers such as propranolol, although they help a bit with the speeding up heart rate, seem to leave you conscious longer.
also question if i vomit a lot of it up immediately should i abort and ask for help?
It is recommended to prepare a second, and even a third drink with 25g of SN (35 if you weigh over 100kg) in case you vomit. If you can't down a second or third glass of SN - which is understandable as your body won't like it - the absence of long-term sequelae due to the consumption of SN make it up to you whether to call emergency services or not. In all probability you won't get brain damage if you don't call for help, so it might be worth trying to see if there's enough SN absorbed by your system to CTB. But you can call for help if you feel like that's the right thing to do.