Tension. I am having the worst problem with tension (upper or lower or both) plus thread breaking.

Question

I am having the worst problem with tension (upper or lower or both) plus thread breaking. Just changing the thread causes tension issues and / or thread breaking. After a lot of time adjusting, the tension works well until the next time I have to change thread or bobbin. My thread is bonded polyester and the size 18 needle.Is this machine heavy duty enough to handle canvas/vinyl?