Hi there, it does sound like he's doing well with the shh/pat, although it would be great if he went back quicker! My guess is that he is a bit UT and his first A time isn't long enough, which can encourage a long NW in the early morning like that. At close to 6mo, his A times should be more like 2-2.5hr. I'd start pushing that morning one out gradually to at least 2hr and then pushing the second one to closer to 2.5hr, as he's not getting a full nap there with only the 2hr A.
It's also worth it to note that it's still very normal for LOs of his age to have a NF or two, so while he may be waking out of habit at 3:30, he may actually be hungry at 4:30-5. Just don't want you to be surprised if he doesn't go automatically to sleeping through. In fact, I don't know of many BFd babies who sleep 10-12hr without a feed before 7-9mo, or when solids are established.