It sounds to me that you may be using the wrong diaphragm and sluice for the penimaster. If you are slipping that easily, you likely need a smaller size. You shouldn't really have to use a lot of force to hold yourself in the vacuum chamber. That is likely why you are getting swelling, pain, and ripped diaphragms andsluices.
Also, after you play around with different sizes and finally get a good fit, it takes a little while to be able to add wearing time as you condition your penis. When I first started, 45 minutes was about the limit I could keep it on, but now I can go for 2 hours (or longer) but I still remove it every 1 to 2 hours to make sure everything is OK and get a little extra blood flowing. I am able to keep it on for up to 8 hours now with small breaks to pee or just to get extra blood flow in between.
Keep experimenting with different sizes and keep the tension down when you are starting out. Then as you get more comfortable and conditioned, you can start increasing time and tension.
You may want to consider something like a Bib hangar and see if you like that. It can be a bit fiddly to get comfortable and be able to hang longer with heavier weight as well.
Just for reference, I gained about .75
Inch with the penimaster in about 3 months, so it does work and is worth it to take the time to experiment and get it right.
Let us know how it goes