Yes, and if you shorten the timeframe enough, there's a chance that it can clear all the cancerous cells. You also ideally would use multiple variations of the therapy to further reduce the chance of a pre-existing escape mutation.
That's how we deal with HIV. No single HIV therapy (so far) is effective enough to suppress the virus all by itself, but a combination of them provides a barrier that is too high for mutations to jump.
Agreed. Assuming it's ultimately proven to work in vivo, I think the endgame of this therapy is multiple guides targeting multiple mutations along with multiple delivery mechanisms (a formulation-diverse cocktail of LNPs + eVLPs [0]?). Sure, tech like [0] is futuristic and fanciful, but so is the tech of the OP, and both will probably reach in vivo maturity around the same time.
[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC8809250/