Hah. That is a different take than what exactly I was thinking. It is close to an option though. I was thinking more along the lines of fighting left over energies left on Snoopy from the dried blood. I had wondered if Mouse was trying to free Snoopy from Loup Garou binding, etc. Though it has been argued the binding Harry tied into Snoopy and Loup Garou should have been wiped away after so many sunrises, sunsets. However, since the Loup Garou curse is so powerful, and we know that blood can keep magic operating, it is possible that some link continued to exist due to the dried blood on Snoopy.
My crazier WAG's involve Snoopy becoming an ancestor of the Foo Dog line due to Time Travel shenanigans involving Harry. Harry bound Snoopy to Loup Garou and cut off some of the Loup Garou's ability to cause harm after police station incident. Then Harry killed Loup Garou with his mother's silver amulet. I estimated that there may have been feedback into the Snoopy doll, and back into whatever entity holds the Snoopy mantle. Human belief in effect creates mantles so there ought to be some mantle of power out there of some 'Snoopy' character. The unlikelier part is the future=>past bit where this event becomes entangled in an origination of the Foo Dog line, the semidivine entity that gave up its divinity to better affect the world.
I wonder when that Snoopy doll will make a reappearance.
Your suggestion that Mouse used a thaumaturgical link to attack the Loup Garou creature is different than what I've alleged. It could fit. My wag's would be small perspective, yours would be a broader perspective. In any event, Mouse was 'attacking' Loup Garou energies I believe. That or the binding on both Snoopy/Loup Garou. I do like the idea that Mouse as a pup was attacking the Loup Garou via thaumaturgically linked Snoopy doll now. It very well may have helped power him up.
It would also fit with the reported WOJL of why the passage would have more meaning on a Reread.