Yes, very similar to my set up. I assume you want to run the 3 of and the rear remotes atthe same time? If so, you need to put your RR valve in series with the three point. RR valve also needs PB which will go to the HP portof the 3 pt. Return for the RR valve can be tied, with a tee, into the tank return port. If you wanted you get a selector valve to attach to the PB with one line to the 3 pt HP in and the other port to the rear QC for the backhoe. This would eliminate the double hose set up from your FEL valve PB port.
The return lines can stay connected together all the time. I will be installing a nearly identical plumbers nightmare on my L4310 this winter. I have most of the parts now, just need to get my machine closer to home.
Did you find the thread on the do it yourself subframe? There is a whole lot of great info there on design and fabrication considerations.