My friend, i understand your plight but please understand our situation...we might give you advice that might make things worse which is NOT what we want...

To me it doesn't sound like the AC joint.

You sound like you have the bicep tendon popping out of it's groove.

It could be due to many different possible imbalances in the shoulder.

As a rule, strengthening your Wikipedia reference-linkrotator cuff as well as keeping the range of motion even in all directions is a good rule of thumb. Bit of a cop out i know but it really is tough to give advice like this.

It is like asking your mechanic on the phone what is wrong with the car.

Or asking your doctor on the phone what to do about the rash that has just come up/started.

I would much rather NOT give you specific advice and ask you to see someone who knows how to deal with these things...

...but my money is on a tight posterior capsule, possibly some glenohumeral interal rotation deficiency due to excessive tightness of the inferior glenohumeral ligament complex.

Your belief that anterior delts are causing the problem might be correct or it might not be. It depends on whether the joint is sitting correctly in the joint or not.

Or maybe you have a glenoid labrum tear...

Or maybe it really is your AC joint (but i don't think so).

I am sorry. Maybe ask someone about the above points?