NO it is not safe to take HCl because it sounds like you also have a Urease positive bacteria in your stomach. It is that which is causing the apparent low stomach acid. It's not that you are not producing stomach acid, the stomach acid that you are producing is being neutralized by Ammonia. When your saliva mixes with food as you chew it provides Urea which is present in saliva for the bacteria to convert to Ammonia. Ammonia is very damaging to the human body! It damages the brain and nervous system and in sufficient quantity, as happens when attempting to digest protein foods, can stop energy production and can make you sleepy.
Your problem is not Candida! Candida could be present in the biofilm with the bacteria but Candida is not your problem, it is the bacteria!
It is that which you must destroy, then Candida will have nowhere to hide and cannot keep spreading from that biofilm. Target the biofilm and bacteria and you will, in the process, rid yourself of Candida.
You can in the mean time, try eating liquid protein drinks. Find a safe protein such as Pea and Rice protein from body building product suppliers. Make a drink from it and swallow as quickly as possible. Spit out before swallowing it and try not to swallow saliva. It's hard but it can be done. As your stomach acid levels rise you will probably find that saliva levels rise. Spit out all saliva while you are digesting your protein. Done this way you should be able to digest protein properly in 2 to 3 hours.
I suggest that you get some pancreatin and take one capsule immediately before the protein drink. Wash your mouth out with water and then quickly wash the pancreatin down. I also suggest that you consume some oil prior to doing this as it will help. Taking some Omega 3 or cod liver oil is a good choice. It should help to limit the bacteria.
Eat any vegetables or fruit as you can without any issues as they do not require stomach acid so the bacteria should not react to them except perhaps for any acids in fruit. However do as you think appropriate if you have a problem with Candida.
Your body does need properly digested protein so make sure that you are getting sufficient. You could have a higher requirement due to the immune system problems and Leaky Gut that is likely to be present.
Best of luck.....you are going to need it to beat these bacteria.