Good analysis on both sides ...
As for your concerns, I am not worried about the completion percentage due to point #3 and his lack of quality receivers. And IMO, he can handle the quick game. He has been said to be good on the whiteboard, so his football IQ is up there. He did look very good in the Senior Bowl.
And I'm ok with him sitting 2 seasons if necessary - I don't think any of these QBs are ready for prime time and I certainly wouldn't throw him behind a sub-par Bills o-line.
But as I've said before, I don't see him lasting past Denver @ #5. Wouldn't be surprised to see him end up there and being able to pick Elway's brain is a big win. I know, I know ... Payton Lynch, Trevor Siemian, Brock Osweiler. But I think Allen is a better prospect than any of those guys.