Looks safe, but I don't see a point. Do you use a lot of sites that don't work in FF? If yes, then why not just open IE. Seems easier than installing something and then opening FF to open IE.
Helps in testing on CollecToons mostly. I try to break the system with two accounts mostly and hate having to turn on IE since it takes a huge chunk of memory for me.. something my laptop can't handle. Plus it saves space.
It will take the same amount of memory to open IE in a FF tab. It is just like IE except instead of getting to IE from the taskbar you get to it from a FF tab.
Most likely you did not get a virus because you were using Chrome and you would have gotten it using IE or FF. There is not anything about Chrome that makes it more susceptible than other browsers. Actually the opposite since it does not allow you to easily install add ons.