I will in some entries try to answer them in one way or another. Due to two circumstances not all my answers will be very analytically illuminating:
- I have a contract with Gambit Publishing which does not permit me to publish any kind of update of the London book. This clause, of course, is subject to interpretations and I don't think it means I am not allowed to publish any kind of analysis on the London System. However, I will be particularly careful now when a German translation of the book is due to arrive soon.
- The main analyst in the London book was Vlado Kovacevic. If there ever will be an update of the book (I certainly hope so) I will consult him or another London expert in order to improve the analytical quality. In the meantime I must do with my own limited resources.
A: There definitely isn't anything wrong with 5.Qb3. Our choice of 5.Nc3 was mainly because that move had been preferred by more and stronger players and because it after 5...Nf6 would lead to positions that White hardly can avoid anyway.
I have not really been able to determine which of the two moves is the strongest. Below follow some lines which should only be the starting point of an debate.
I will start from the position after 5.Qb3 Qb6 6.c5 Qxb3 7.axb3:
(even if 5...Qc8 really should be taken into consideration too)
I think you are right to consider this the critical move. 7...Bxb1 8.Rxb1 Nd7 9.b4 a6 of Bistric-Velikov, Rijeka 2001 must be somewhat better for White.
I am not sure whether this is better than 8.Nc3 (which gives up the Nd2-b3-a5 plan) or 8.Nf3 (which after 8...Nf6 would lead to known positions), but it can be argued that it's White's most consistent course and therefore should be investigated first.
I believe this must be stronger than 8...a6 9.Nd2, planning 10.Nb3 which should be at least somewhat better for White.
Again this seems the most consistent but 9.Nc3 and 9.h3 are serious alternatives.
There are some interesting complications after 9...Nh5 10.bxc6 bxc6 11.Bc7 Rc8 12.Rxa7 but they seem to favour White, so I assume this must be critical.
How should this position be evaluated? I am not 100% sure, but it seems to me that Black's active pieces should ensure him at least equal play.
So my tentative conclusion is that 5.Qb3 probably is a good move but that White shouldn't try to make it an independent continuation but rather follow up with normal development. And if that is correct it seems sensible to play 5.Nc3 and not force matters before something concrete can be achieved.
I will return to the rest of the questions in due time.