Is there any mid / low-level counterplay to getting harassed by Dream Message / Nightmare / Sending / etc.?
As others have pointed out there aren't many if any on Golarion. If you're willing to use third party supplements then Drop Dead Studios (the people behind Spheres of Power) has a setting called Skybourne which is all about floating islands. The setting is for 3.5/PF1 so you may need to update a few things. They also have a book called Ships of Skybourne that details building all sorts of vehicles, mainly airships but also land and water craft too. Personally I'd love to see an update to PF2 especially since we now have the inventor class.
Interface Zero, a third party supplement, has a medic class that you might want to look into. It's a cyberpunk world without all the magic of Starfinder, but you can add magic in easily enough. I recommend it because in the NPC's section there is an android medic called the"Medi Andi" which was a corporations attempt at creating a medical assistant and your concept reminded me of it.
I agree about the third party products. One you might want to look at is Interface Zero. It'a non-magical cyberpunk version of Starfinder. It has a number of races similar to what op posted. It does have a psionic class and archetype, but those can be ignored if you want. It could make for a more "science" and less "fantasy" version of Starfinder.
I would like to see a Player Companion about constructs. I'd specifically like to see some more about animated objects and some new construction point options. Also, more on the Craft Robot feat (in the last volume of the Iron Gods A.P.), for example how much does it cost to add some of the various options mentioned to robots- does it cost extra to add a self destruct option to a robot or does it increase the CR. Something along those lines. Maybe we could get a new Archetype that focuses on building constructs. I'm aware of some third party suplements and the notes in Ultimate Magic but I'd like to see that expanded into something more.
I've got a few questions,sorry if they've already been answered.