The biggest reason for your confusion is that you choose to use unknown steel. While a rule of thumb would indicate and old truck leaf is 5160, there are no guarantees. If you want to eliminate the confusion buy known steels from places like NJ Steel Baron that cater to knife makers. You...
Stainless steel and non-stainless steels used for knife making all have high carbon levels - Your are debating non-stainless versus stainless, I presume?
vinegar is acetic acid, so you do have access to acid if you can get vinegar. Most use ferric chloride/vinegar mix here is USA. Search youtube as I recently saw a video on making ferric chloride. I'll post link if I can find it..
Here it is: https://www.youtube.com/watch?v=PkW0XotNmYo