I'd still recommend keeping it. I think astronaut autopens are interesting collectibles. It's something that came from his office over 50 years ago, and will never be available again. Secretarial signatures and forgeries are worth less than nothing, but autopens have a real (if indirect) connection to the astronauts.
As for the others, I think the signed envelope is definitely real. The handwriting is a good match. But I'm just a fellow collector, not a signature expert. Especially with Armstrong autographs, I recommend sending them to Steve Zarelli for full evaluation. He charges about $100 for a full Armstrong evaluation, but his certification will increase the value of the signature by at least that much. Armstrong signatures with a Zarelli COA sell for hundreds of dollars more than those without one. So it pays itself back by increasing the value of your collection, and it gives you peace of mind knowing that it's real. I sent in my entire Mercury/Gemini/Apollo collection, and I'm so happy I did. Steve does great work, and there's literally nobody in the world with a greater expertise of space-related autographs.
At the very least, I'd recommend sending the two signed paper items for email evaluations, with a full evaluation for the photo. Lunar surface photos signed by Neil are very rare, and worth a lot more than his regular autographs.