A clear example of how ineffective this would be is the "We the People" petitioning system that was created under the Obama administration. Anyone could create a petition and sign one. Responses were often quick and dismissive unless they aligned with the goals of the administration.

https://petitions.obamawhitehouse.archives.gov/

Basically, real change isn't going to come from a few megabytes of text. It would be better to start or join a charity, a lobbyist group, or some other real-world action.

No. That'll just fuel propaganda machines saying that the support is artificial. Let the people speak for themselves.