Have a look at this other post of mine discussing pressure, pressure reducing valves, thermal expansion, and thermal expansion tanks. Hopefully, it will help you understand what is happening in your system.
http://www.homerepairforum.com/forum/30657-post8.html
If the relief valve you have is opening at less than the set pressure it has failed and needs to be replaced. If you have a high pressure it is doing its job and you need to treat the cause of the problem.
The problem with push fit connections like gatorbites is they hold but allow rotation. I prefer connections to be ridgid on all planes. If you do install using a push fit connection I would recommend sharkbites over gatorbites as they are removable while gatorbites lock on permentently.