Cisco Routers :: Cascading RV180 As DHCP Server But Pointing To Another Default

My network topology is as follows:
 
Internet <-> Residential Gateway (RG) from ISP (OEM: Pace) [192.168.1.254/255.255.255.0] <-> RV180 [192.168.1.253/255.255.255.0] <-> SG500 switch [192.168.1.250/255.255.255.0] <-> rest of network.
 
I know this is a cascading LAN-to-LAN arrangement. The cable from the RG to the RV180 is from a LAN port on the RG to a LAN (not WAN) port on the RV180.
 
I eventually want to segment my network into a few VLANs from the RV180 down. I am aware most people would recommend DHCP on the "primary" router, but the RG is non-VLAN aware, so I figure I need to handle the DHCP off the RV180. At the same time, I have also opted not to do a LAN-to-WAN cascade because I want to retain the ability to configure the RG from the rest of the network and not have to cart a computer over to the RG to do it.
 
On the RG, I've disabled DHCP, and placed 192.168.1.253 in the DMZ.
 
On the RV180, I've enabled DHCP and put it in Router mode.
 
The issue is that I do not have any Internet connectivity. If I allow the computers in the network to receive IP addresses over DHCP, the default gateway that is communicated is 192.168.1.253, which is the RV180. If I configure static IPv4 information on my computers to point to 192.168.1.254, I am able to connect outside, as you would expect.
 
How can I get the RV180 to pass out DHCP IP addresses, but point to 192.168.1.254 as the default gateway? I thought the solution might be to create a default route (or something). I went to the static routes tab but it wouldn't let me enter 0.0.0.0 as a destination IP to route through 192.168.1.254.
 
Further down the line, is it possible for both the RG and the RV180 to connect directly to the SG500, along with the other nodes in my network? That way the RV180 only serves to maintain the VLANs and pass out IP addresses via DHCP, instead of having it be the choke through which everything goes through on the way out?