Your z-wave topology as small as it is looks fine but overall you have some weak points in your mesh. This is indicated by high route changes. You can see high RTT (Round trip time) You could probably do with a few beaming repeaters. To get a better handle on the way the signalling works, I would go here... gives a decent intro to z-wave... Learn - Z-Wave
For rssi @JasonJoel has a good comment here about it. Essentially it depends on things Z-Wave LWR RSSI dB value question - #3 by JasonJoel
