I don't get the multiple buffered multiples, either. Or the need for two Pam's, as there's more potent methods for manipulating clocks and deriving Boolean gate sources to REALLY complicate the clock functionality.
As for the power question...yeah, this will be OK in that aspect. Note also that Eurorack uses three separate power rails: the + and -12V and the 5V rail which doesn't often come into play but is still necessary for certain digital modules. The only time the 12V rails MIGHT come together would be at a common P/S groundpoint, but they have different supplies on the "hot" side. But the rule of thumb for dealing with current inrush is that the P/S should be capable of supplying 20-25% MORE current than the module complement (roughly) requires, as getting too close to the current limit carries with it the danger that an inrush on switch-on could cause component damage.
One other point: this is really a rather small build, but there's a number of bigger modules in this. Naturally, this limits any further expansion in the case...but right now, it's locking you out of making adjustments to the module complement. This could be done a lot more effectively by trying to replicate the functions of those large modules in smaller ones...this should be possible. But also, some of this is simply redundant, like the thing with the Pams'.