On my Arrow, the firewall has four "tabs" about 1/2" long, one at each corner of the firewall, that fit into corresponding notches on the side of the fuselage. So where your notch went is an interesting question. For some reason (and it may be the camera angle) the distance between formers seems a bit short. By some chance, could you have lost a piece of the original fuselage that had the notch?

In the end, it probably won't matter, especially since you've already expoxied things together. I assume you're going to reinforce the firewall/fuse joint with some triangle stock? Another thing I did when I rebuilt from a similar crash was to put a piece of 1/16 ply on the inside of each fuselage "cheek" in front of the firewall. That way I made sure the firewall wasn't going to pull out of the plane, and added some rigidity to the cheeks as well.

I'd be very careful with your receiver. I've had them check out in the shop, and even with a running engine, but when I put the plane on the ground a did a control check, nada! That looks like a JR receiver... usually you can send them back to Horizon and they'll check them out for you. It would be a shame to get the fuse rebuilt, recovered, and then lose it to a radio glitch.