No, no, yes
Only the ressources can be tracked via event
Code:
EVENT_POWER_UPDATE (number eventCode, string unitTag, number powerIndex, CombatMechanicType powerType, number powerValue, number powerMax, number powerEffectiveMax)
Add a filter to the event so it only applies to yourself (unittag: player), described here:
https://wiki.esoui.com/AddFilterForEvent
And maybe only track the stamina CombatMechanicType (powertype).
But how much stamina the bash costs is maybe not a fixed value! Not sure if one can determine this at all, I doubt it.
Depending on your race, class, passive skills, equipped skills it may cost more or less stamina to bash.