To take each of those in turn....
10/11. I would say that VDV was not available (especially not to us) until the last day of the window.
11/12. I think we could've got Parker earlier, but I don't think it would've altered either of the two results.
12/13. I think we missed out badly here and securing signings earlier would've been likely to have resulted in us winning more points. I think all three players could've been secured earlier in the window as well. I think in this instance not doing our business earlier probably cost us qualification for the CL in place of Ar5ena1.
13/14. I'm not sure that we could've done any better in that window really and I don't think signing Eriksen earlier would've made any positive difference to the start we had that season.
14/15. We did our business early, but as far as I remember none of the players we signed actually played in those early games - so I don't think you can link doing the business early to getting early wins?
15/16. I think we have probably missed out on 2 points (possibly more) so far this season by going into the season with only one striker. I think our initial move for Berahino should've been made earlier.
I agree with a lot of what you're saying.
10/11. He wasn't for sure. But I can't believe we didn't spend more this window given that we had CL
11/12. I think we would have conceded less, and might have gotten points. We were a completely different side once Parker joined.
12/13. I agree
13/14. We were very lucky to win those first two games.
14/15. Who scored the winner in our opening game again? Also, in this window we didn't lose any key players.
15/16. Given how many times we've been one or two points away from cl, I'd say that's quite a big deal.