On your last point it's clear to me not the best option. But has anyone made signature campaign their main source of income?
With no other work like being unemployed, I think it's fine to make signature campaigns the main source of income (for a while). But when they leave their main job and rely solely on signature campaign as source of income, it's clearly a bad decision.
There must be and probably more than you think. Those who make signature campaigns their main job are not without reason. As the same said before, they made signature campaigns because their jobs were unilaterally dismissed or couldn't find another job or there was no job call, so being on the forum and being a good contributing member became a last resort even though there would be some opportunities for other real jobs. Whether it is a bad decision or not depends on how to manage the salary received from the signature campaign. Saving some of the salary received for some other ventures or for investment is highly recommended, or also holding the payment in BTC for a long time, just like doing DCA for the long term.
The signature campaign may be ending, but there will be a replacement. The forum continues to grow and developer requests for advertising on this number one bitcoin forum will probably continue but with a different mechanism.