The 400 Blows is definitely a masterpiece. I'd have to disagree with you though about the Blu-ray transfer though. The Blu-ray is so much more detailed than the DVD, and contrast is better preserved.
I know what you're saying about the final shot of The 400 Blows acting as a perfect end to the Doinel story, but Stolen Kisses and Bed and Board are definitely worth checking out. They make a nice double feature. Antoine & Colette is also nice, but slight. If I could erase Love on the Run from my memory, I would. On the DVD supplements for Love on the Run, Truffaut even mentions that he wasn't satisfied with it and found it "too experimental." The Doinel saga ends with Bed and Board for me.
After Bed and Board, check out Day for Night. It's probably the greatest film about filmmaking ever made, and lends a lot of insight to the Truffaut/Léaud working relationship.