I feel ya, man. I've certainly had some challenging ones, it's true - and the initial rush seems to trigger my fight or flight response everytime. I don't think I've ever cried out in panic, or thrashed around or anything, but I very often have the feeling (initially - and even throughout) that I've made a really fucked up mistake and just don't want this anymore. Now, I've got set and setting issues that would put Timothy Leary on the wagon, but we each bring ourselves into the experience and we've all got some shit to contend with.
If you want to continue, I find that a sleep mask can be extremely helpful. The biggest source of panic for me is in straddling irreconcilable planes. Anything I can do to aid in letting go of this one will only help me settle in and fully commit to the other. Sublingual harmalas in conjunction tend to physically pin me down, so that might stop your wanderlust (and possibly the screaming...), but they can also ratchet up the intensity, so go easy with them initially.
It is much like having an atom bomb go off in your head, as you've described. I can't think of any greater test of one's ability to surrender. But when you can, Jesus Christ... it is just SO fucking beautiful. The discovery of the mystery within (and all its infinite implications) has been one of the most profound events of my entire lifetime.
Having said that, there is ZERO shame in deciding to call it a day. You've seen what's there. Now you know. You have nothing to prove to anyone.