Grants from NLnet are flexible in terms of timing. You will be able to start working when available, even if this means three months after being awarded the grant.
You are already part of the team 
But there is no need. It helps if you have connections with people and organizations related to your work, even if not a member.
IMHO it is likely. You have a very rare skillset and if you make a good application this should be seen as a considerable asset for the project.
You would be better off apply for a grant to contribute to forgefriends or Codeberg. In the end it is the same codebase but different organizations / projects.
The payments are philanthropic donations from NLnet and tax free.
Hope that helps!