Tunnel on cellular modem: high data usage + shuts down

We are using tunnels successfully at 3 customer sites via cellular modems/Twilio SIMs. Is IoT with some user interaction. We assign each to 2 subdomains, for HTTP and VNC Application access.
Are there settings to help with these? We haven’t found any. 2 issues:
1-- Just running a tunnel (very little real data) uses nearly 4MB/hour, which becomes expensive. Any way to reduce that by 50-70%? OK to have only 1-2 connections vs the standard 4. Also OK to have much less what we assume to be “heatbeat” traffic. (We had tried ngrok which did not create this usage but worked fine.)
2-- Power outages at 1 site occasionally take the cell modem down for 2-60 minutes. The tunnel process then just dies - don’t have details yet on when or log output (site is inaccessible!). It should just patiently wait & reconnect when possible.
Thanks for any assistance.