I am curious if i could try to test myself for the SN method. I know it's hard to drink it and not vomit, so is it a good idea to try drinking salty water to check if that would make me vomit? If not that is there another method to check your "endurace" like that?
Don't test with SN itself under any circumstance. There is a sticky thread that warns about not testing SN ahead of your CTB because a dose as low as 2-3 grams can be lethal. Some members have shared their stories of going to the hospital after doing a test run with SN.
As for testing with salt: sodium nitrite is 33.3% sodium and 66.7% nitrite; a portion of 25g contains 8.3g sodium. Salt is sodium chloride, which is 39.3% sodium and 60.7% chloride, so you would need 21.2g of salt. This is equivalent to 3.7 teaspoons of salt.
The solubility of salt in water at a temperature of 25C is 36.0g/100mL so you can dissolve the 21.2g salt in as little as 59mL water. You can round this up to 65mL to account for minerals and impurities in the water affecting the solubility of salt.
Don't have the salt with a meal (or shortly before or after), otherwise you'll retain it and feel uncomfortable for hours.