5036 5975 registered at ASL Scenario Archive (but I think it's 500 not registered yet). All the AH/MMP ones, except the ones in Hollow Legions. Take in account that there are duplicates: Paratrooper. Partisan!, etc. How many from TPP? I don't know. To your fourth question, I'm not a completist; so, if scenariors appeal me as a prospective attractive scenario, I'don't say no to it (for instance, I want to play Westerplatte sequencially, or Maxim Gorky), so no, I don't think how many scenarios are too many. Another interesting thread could be: "How many maps are too many?", because I feel that there are many maps underused and brought on to support a couple of scenarios. I feel that, at the moment, we have all the maps that we need, and I would go for the same maps PTO, DTO, and Steppe (if anyone, anytime, dare to design an scenario pack for the steppe terrain). Interesting questions, BTW, only wish I could answer them with more precision.
Best wishes.
Edit: This thread motivated me to not being lazy and update my acquisitions into ASL Scenario Archive!