I'd look up nooblets solo build on pvp, it's not prim plus but will give you ideas for outside defense, bear traps and large traps if they available would be real good to slow them down.
Man if I get back on I think I'm going to get on a prim plus pvp server. It is so much easier to defend when you just need to keep people far enough away to prevent them throwing oil jars.
You're inaccessible to land Dino's. I would build a fat plant x tower up from your roof to prevent a pair hanging over your base and flaming from above.