Please Help - How Do I Dilute HCL - My Dog has Cancer :(

Greetings fellow truth warriors!

I was hoping my first post to this forum would be more upbeat, but sadly I could use some help with an urgent matter. My 7.5 year old furry best friend Riley (Half Lab, Half Pit) was recently diagnosed with a form of urinary cancer back on 6/4/20 and the Vet said he had anywhere from 3 to 6 months to live at best. They advised against surgery because the cancer is in such a difficult place to reach that one wrong cut could have serious implications. The tumor(s) is/are creating pressure on the surrounding organs that has strained his urethra hence he sometimes has blood in his urine.

I've been administering to him 8 to 12 activated drops a day (SC + 50% Citric Acid) using various methods because he refuses to let us squirt any form of solution down his throat. The only success I've had is activating 4 drops inside a pill capsule and hiding it inside a piece of deli meat or mixing 2 drops into a chicken broth with pieces of chicken. At first we saw light improvements where his overall mood and physical activity improved, his urine had less blood and he was eating again... but in the past 7-10 days his behavior seems to have declined again and he's avoiding about 75% of his food again. Note: We took him 100% off kibble and he's been on a raw meat/bone diet or cooked chicken meat with sweet potato and spinach since diagnosis.

I've been at this for 2 months now and I want to take it to the next level in being more aggressive with his treatment. The 50% Citric Acid as an activator has been a nightmare to work with so I finally ordered some Hydrochloric Acid 6M (Lab grade) directly from Carolina Chemical Company. The back of the bottle label reads: Water (81.2%), Hydrochloric Acid (18.8%). How do dilute this to the recommended 4% strength? I want to make a 200 mL solution.

Also, I'm interested in doing injections on him as there seems to be a high success rate using that treatment. Can the injections be subcutaneous or do they have to be intravenous? The reason I ask is whenever the Vet administers shots they seem to do it so fast with no resistance by doing subcutaneous injections. Where would be the best place to inject the solution to attack the urinary cancer? What strength/dosage/frequency would I use? He currently weighs roughly 65 lbs. Finally, before I administer any shots to him, I want to first test myself. Where would be the best place to administer self-injections?

I'm sorry for the long post. I love my dogs to death and I refuse to give up him, especially since he's fairly young and I want this to conclude in a successful testimonial. I sincerely appreciate any information you guys can provide in advance.