I had a similar issue with my JP Blue Dawn after I purchased it. It turned out that the bar itself was too thick where it goes into the slot. Because the guitar was previously owned by someone else I contacted customer service and they sent me a new one for a small price. If you're near a retailer that sells Music Mans and have some Petrucci in stock, I would take your guy there and see if the bar on the other guitars fits yours.
A lot of force! But I would not necessarily recommend doing that if there's an alternative. My guitar had already been back to the dealers twice and a third time wasn't really an option for me.
Depress the trem, and loosen the screw you see behind the bar on the back area of the trem that becomes visible due to it being depressed. If it still doesn't go in, then I think it might have something to do with the bar.
Glad yyou know your issue and it will be corrected so all is good. But I had the same issue with my JP and could not get the bar out for a few weeks and was afraid I was going to break something. I finally said the hell with it and put my hand palm down over the bridge with the bar in between my middle and ring finger and pushed down and pulled up as hard as I could and-Pop. After the initial removal it goes in and out as easy as pie though I don't know why that first time is so hard?
Understood. About how much space is left around your bar? My bar has at least 1/8 plus around the entire perimeter of the bar. Also it has a white threaded tip on the end of bar. Never seen one on the mystic dream.