98 LPK Questions

SO i just got to use my 98c w/ the low pressure kit installed. I also have the e-grip and flatline on it. It was awesome and shot far and straight. I have a few questions though if someone has a moment to help me out ....

I use a 72cu 4500psi low pressure tank. Tank puts out 400 psi. Now i also have some junky looking regulator someone gave me with no name on it. It was all set to about 350 psi or so. So that part was great till i ran out of air.

Then i hooked up another nitro tank that was probably not low pressure. When i hooked it up to the reg the reg leaked like a siv. So i screwed it right into the elbow (where the reg would be) and took a few shots with it. It was crazy!! So far so fast so straight. It was so hard i decided not to use it in play cause it would hurt too bad to get hit with it and it just didn't seem right. Mind you we play in the woods with friends and no chrono.

Was that really bad for the gun? Being it has internals meant to fire around 300 - 400 psi. Also when using a low pressure tank (400) psi do i really need a regulator since the tank psi is what the gun should be shooting at? Is this a case where i can use a gas through thing (forget what that is really called)?

Any help would be greatly appreciated.