Keep with the swabbing routine.. it sounds like that is going to help you. Some times rifles just do not like certain projectiles, no matter what. All you can do is change them out to something else. I think I would start with 100 grains and the 250 grain Shockwaves. I think this will give you the kind of accuracy you need. Owning the rifle you do, I really think you could push them to 150 grains of pellets or even 120 grains of loose and still keep the accuracy.

After you have an established load, then when you have time, go out and try everything and anything that draws your fancy and see what you can make it do. As for the broken sabots, it happens all the time. I never had a problem with accuracy from it. Although like you I can remember questioning members on the forum about it also.