FOSS gamedev and creative worlds

Is there a setting to allow pvp and damage to everyone but select players?

no

Can the fast speed be altered so it is not as fast? toned down to like 2 or 3x the normal speed?

Nubelite wrote:Can the fast speed be altered so it is not as fast? toned down to like 2 or 3x the normal speed?

I don't think, without a client mod.
You'll have to wait for vehicles :')

This one is a server question for performance. how much does the map size affect the latency of a server? If the map was only 5000x5000 vs the 30000x30000?

or if it can be done, x,z=-5000 to 5000 y= 500,-5000

Map size doesn't affect the resource usage of a server (except disk space of course).