The pump should be fine. Slowing helps with less adequate pumps. You test shows no more than the hose is clear. I am assuming the car was hot. It does seem as though you are sending fluid to the overflow but two items I mentioned about the cap or the tube earlier may be an issue. But to be honest, I forget the exact procedure for testing the vacuum recover since it has been so bloody long since I had to test one. The system is full, the overflow level rises when hot, lower when cool, looks good!
I disagree on the block pressure and velocity. With that said, don't raise the block pressure unless you need to. If you increase velocity you reduce pressure which reduces boil point with increases the chances of steam pockets. Fluid dynamics. At the wild end of the scale it is possible to pass coolent over a surface so fast that inadequete thermal transfer occurs and the coolent becomes ineffective. It takes time for the transfer to occur. What period of time that is I have no clue
