The sticky jam is probably a better idea than the flat tire, due to the lower risk of real damage. Issue would be to make it really uncomfortable while still being easily accessible for the protestors. It has to be as uncomfortable as the tire. But I guess the goo could easily produced at home from household supplies.
There will always be cases of collateral damage. You won’t be able to safe the climate in such a big and complex society without disadvantaging some people.
Maybe one possibility for your wife could be to measure the cleaning equipment and see if it might fit into a smaller car and potentially buy cleaning equipment that is more foldable that might fit. Usually even these small cars have a lot of space when using the back seat row. A big vacuum and mops should easily fit. If this is not possible then I completely understand your problem.
The bigger issue I see with this is that, when your wife would do everything to save gas, she would need to take some disadvantages, e.g., more uncomfortable to load the small vehicle. If there is no pressure for other people, she would be the only one doing it, making it unfair. That’s why it is so important to generate pressure on climate damaging behaviour on all fronts. And this action is one efficient and realistic way to achieve that. But of course you can make the movement more unpopular in the general population… It is really difficult to find and decide for a solution here…
A truck is not an SUV.
The issue is that an SUV is probably never needed, therefore everyone can trade it in for a more reasonable car.
I don’t think it is only because of disinformation. Our modern day consumption is desirable on its own. I don’t think you need disinformation to convince people that flying to a sunny and exotic location is desirable. Or the flexibility and mobility that driving thousands of kilometres per year in cars provides. Eating meat and drinking milk…