Hrmmm... AFAIK, there has been no Dresdenverse material suggesting that magic can work that way ...  At least, not mortals' magic.  I s'pose some of the immortal beings -- who are force-of nature / force-of-magic / must-be-true-to-their-natures sorts of beings --  have shown a few hints that they can "do magic" just by doing their normal and nominally-mundane activities....

I'm pretty sure we have seen common rituals working that way, it's only when you are drawing up the power, in part, from yourself that you seem to absolutely need to shape it through your own will, it's just that without intent, external power tends to dissipate. In the case of warlock executions, there is a lot of group intent, and rather more than a drop of power being released.

And yet it's what they are actually doing, intentional or otherwise, they promulgate and evangelize the Laws and execute those who they believe violate them. That is a lot of power going in to making the Laws real. We already have evidence that non magical acts stain the soul gaze vision, that you become how you behave, the only things really special about the Laws is that you can get power out of them and the White Council's Wardens enforce them. We also have evidence that they can be bypassed or at least, that the damage can be insulated against or redirected, though we the exception of the blackstaff, we don't really know the mechanism. Now it may be the case that the power associated with Law Breaker would be there without the White Council's Jihad, that the acts would be specifically twisting above and beyond their mortal equivalents, but so far we only have correlation, and we know we have an unreliable narrator.

Conditional stress boxs should probably go at the end, otherwise, the value of your base stress boxs is variable and you get some weird cases where your extra stress boxs 'matter' even when filled.

I'd personally implement it as follows:

Multi Evoker [-1]
You may split the power of your evocations among multiple distinct effects, making a single control roll for the combined power of all effects. Power devoted to duration is shared by all relevant effects. The targeting interpretation of the control roll is split normally across the distinct attacks per evocation Spray rules.

This doesn't end up boosting pure offense/alpha strike, but should allow a WR 1 attack to be mixed in with a maneuver or block. Note, be very wary about lifting the spray splitting rule (consider power 4 split a a WR 1 direct attack and a WR 1 zone attack).

If the targets aren't taken out, then the follow on consequences don't come into play. As the total strength of the poison attack is your fists rating, high endurance and a bit of toughness are going to make the Poisoned state mostly irrelevant. If you can strike and disengage without substantial resource expenditure and without time pressure, whats stopping you from just taking them out in the first place (possibly one at a time)?

As for 'when' the monsters shrug it off (assuming they aren't taken out), they shrug it off at the point where the make a maneuver roll sufficient to remove the Poisoned aspect. If you are lucky, they will spend a consequence to help make the roll, but as you've disengaged, the only thing they have to worry about is the poison itself, so, to some extent, they are at their leisure to maneuver to provide enough tags to remove it (be those endurance maneuvers, magic, survival, etc).

The other other other option is to do the normal summoning/binding/controlling action in the background and do 'combat summoning' as a maneuver to bring one of your already contracted allies to the battle.

And natural weapons are almost always enhancements to Fists attacks.