The basic shopping list of good stuff from R+H (in my opinion)
Wyverns
Griffons
Quad mortars
Eathshakers/medusa platforms
Rapiers
Plague zombies
Spawn
Infantry platoons
Hydras (unless you just fancy ignoring all air)
Seems like you're pretty well on track. Then you've either got the choice of master of horde or ordnance tyrant, both of which have their pros.
You havent actually shown us what you're taking in terms of the infantry platoons.
1 wyverns are great. Griffons and quad mortars are also good.
2 I'd consider some earthshakers + medusas in combination with them. The RLDs are good though.
3 You'd need to move to get to backfield objectives? The UH should help with that though
4 some of the above