I'll have to check the comprehensive rules later on this to be sure, but I believe you are correct. It has become the target of a spell or ability three times, specifically because it did BECOME the target of the spell again.However, for your third situation with
Twin Bolt, reference this from the Insidious Will rulings on Gatherer:
Quote:
The copy will have the same targets as the spell it’s copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for one of the targets, you can’t choose a new legal target, then it remains unchanged (even if the current target is illegal).
So, in this case, you haven't actually changed the targets. Both are still the targets of Twin Bolt, which you then divide the damage as you choose, so the game sees the targets as having been unchanged, and the Silverfur Partisan's ability will not trigger again.
EDIT: Between my second part and adeyke's comment, yeah, the Silverfur Partisan REMAINS the target of the Brutal Expulsion, even if the mode that it was targeted by has changed, so it won't trigger three times but only twice even in that situation.