I have two questions:

1) How can I setup a permanent static route?  I have a node with the LAN in direct mode and a router on that subnet I want to be able to route through to reach other internal networks, and possibly the Internet. I have established the route using 

ip route add 192.168.4.0/24 via 10.224.74.98

But I would like to make that permanent. I have looked through the OpenWRT docs but they seem to differ in syntax. Any pointers appreciated.

2) On the LAN subnet noted above, the router has a static IP Address. I can easily "map it out from the DHCP pool by entering it as a static assignment in the DHCP setup. But, then it is advertised as being a local service. Is there some way to adjust the size of the DHCP address pool to contain less than the full 13 addresses?

Why not plug that router in via a WAN port instead? You would need a smart switch with a Ubiquiti to do this, or could use a Linksys wan port direct.

What happens is the node routes all traffic destined to non mesh addresses that originated on the LAN to the WAN port (even if your not a mesh gateway) and allows you to access those networks.  (note: a bug was fixed in 3.0.1b01 where the node would in certain cases accidentally prefer routing over the mesh instead of from LAN to WAN)

Beyond that the DHCP pool and options are covered in OpenWRT Docs (you might try looking at the configur folder) and in our source code Exact methods to make changes depend upon what device (Linksys or Ubiquiti) due to the age of the operating system on Linksys. Same is true up at OpenWRT as the methods change over the years as the operating system evolves.