Sean, I had the same exact issues you are listing above when I tried to use my MacBook Pro with Parallels. It works great for all other windows software but it just does not play nice when using Das Trader Pro with multiple screen and multiple Montages. When I was using just one screen (the laptop screen) it was more stable. Once I added other screens it just didn't perform well. The default template would sometimes not stay on the multiple screens so I would have to set it up to fit correctly. In rare occasions the software would freeze or not respond. Once this happened several times when I was on the simulator, I called it quits. I did not want to go live with a system that was not stable.
My suggestion is to invest in either a PC or a laptop. PC are cheaper and give you more bang for your buck, easier to set up multiple monitors and easier upgrade in the future. I took some of my capital I had saved up for trading and invested in a good PC system.
Hope you find a good stable system! One less thing to worry about when you are 100% focus on trading.
Carlos M.