I'm not sure I follow what you are doing, but I think you are trying to use FBF (Filter based forwarding) to force layer 2 traffic through the transparent SRX firewall. This will not work as FBF is fundamentally a Layer 3 operation.
To use a transparent SRX you need to insert the SRX in-line with one of your two devices instead. Disconnect the cable from one PC to the switch and insert the SRX in that line.
You then write the SRX rules such that they allow all traffic and process the rules you want between those two PCs