GLO, in your 2 diagrams, one.jpg is NOT possible, you MUST use 2.jpg. The 2 FWs do NOT act as one device, which would be required for one.jpg. Instead the act as 2 separate, but redundant devices. The EX2300 VC DOES ACT as one device. So the solution for you is to create 2 separate LAGs on the EX2300 mixing interfaces from FPC0 and FPC1 into each LAG. Then you also need to create 2 separate (again 2 port) LAGs on the FW's.. Whether or not LACP is also required, would depend upon FW vendor LAG implementation, but would be a suggested best practice configuration.
Hope this may help you.