While I can't answer your specific questions, I would note that while the concept behind the G0516 may sound attractive, it may not turn out to be very practical. You may find that you get tired of constantly setting up and tearing down fixtures when you want to switch between a milling job and a turning job.
If you had a separate milling machine, then you could do the occasional milling job without changing your lathe setup. A lot of G0516 owners seemingly end up removing the milling head and buying a separate X-Y table and base for it.
So you may do better by getting a G0602 and then waiting for a 25% Harbor Freight coupon to come along so that you can get an X2 (HF 49991).
Although another consideration to take into account is that Grizzly always seems to be backordered on the G0602.