Well bitter rot and scab can be controlled by captan. I have attached a link for a short article on apple scab control from Purdue University. It discusses using captan and other chemicals to control it. Since captan also works on bitter rot it would be a good choice for you.
The main disadvantage of captan is it breaks down quickly when you add it to water that has a pH above 7. So in many cases you will need to lower your water’s pH before adding captan. Well water or city water is often above pH 7. Usually people use citric acid (usually found in the store with canning supplies) or vinegar. I have added links about the pH issue and how to adjust the water below.
I am curious about your scab problem since both Jonafree and Enterprise are highly resistant to scab. I wonder what in the environment makes scab really bad for you or if maybe the condition on the leaves just looks like scab and is caused by some other organism.
https://www.extension.purdue.edu/extmedia/BP/BP-1-W.pd
-mroot