Well now, firstly the difference gain in shield block when you switch from Bulwark to Savage wall should be between 0.5% and 0.1% block (depending on how much shield effectiveness you have on other bits of gear). That's not really a number to get your panties in a twist about (considering most guards will sacrifice waaay more survivability than that in other gear to help hold aggro).
Quite how Savage Wall gives 2% more parry than Bulwark I don't know, it doesn't have any parry skill on it and certainly doesn't have any native parry bonus. Are you sure it's not that you forgot to put a balanced strut on your Bulwark? (Even then that's only 1%...)
As far as I'm aware the transfer from Bulwark requires the shield to be equipped to work, I'm pretty sure I remember them patching that ages ago.
It is a transfer, like swashy, coercer or assassin transfers and does not need to be reapplied except when the duration expires. It is well worth telling the lowest hate generators to cancel the buff on themselves though as you only gain the benefit of 50% of incoming transfers, so if you have the coercer transfer and assassin/swashy transfer just get everyone but the scout and coercer to drop the aoe transfer effect manually, that way you get most bang for your buck.
The only shield I personally would use over the Bulwark (if I had it

) would be the Shield of the Dwarven King (off Avatars).