Here's some info on r152a. It was recommended by the EPA over r134a during the r12 phase out process. As a drop in replacement, you will lose a little capacity versus r134a. Maybe 10 percent.
Check out the graphs and this article:
https://www.kth.se/itm/inst/energite...del-1-1.686423
If you're looking for quick and simple, the r152a is a single substance. Since you have a leak, using a mixture is sketchy because the more volatile substance (propane in this case) will boil off first whenever it can. Also, since isobutane has a boiling point around freezing, when the mixture becomes mostly butane, you could end up sucking air into the low side if that's where the leak is. With decreasing mass in the loop comes decreasing suction pressure, so at a certain amount of leakage, the evaporator circuit will be operating well below atmosphere.