Bspamail Hello, and welcome to GrapheneOS! Recent user here as well. I'm just going to address your point #3. I'm using Gboard, but without granting it any permission besides sensors. This allows using the enhanced predictive typing & swipe capabilities of Gboard, but without it sharing data with the mothership as it doesn't have network permission.
There's also a clever way to enable offline voice to text typing here. Gboard will need to have network access for the following, in order to download a required database file. Go into the Gboard app & enable "Faster voice typing" then wait a little bit (I think I left it on for 3-5 min or so, though I've seen on this forum other people needed more time) before disabling network permission. This enables voice to text, which I've found to be quick & reliable so far.
GrapheneOS is getting better all the time, and I am also extremely grateful to all the talented people making this happen.