Hello Paul,
Your ping times to your remote site seems quite OK, mostly under 100 ms. The few spikes to 150-200 ms should not be much of a problem if you configure 'Advanced settings' and 'Keyer settings' in the RemoteRig boxes. Values for 'Keyer settings' is in the manual and if I recall correctly the delay should be similar to the ping time so try 100 ms. Here on this forum Mitch, DJ0QN has given recommendations for 'Advanced settings' for 3G. However your 4G/LTE is much better than a 3G connection, so I don't think you need to increase 'Advanced settings' that much.
I have set up a PingPlotter checking from my QTH here in Denmark to your remote site and I get quite stable 200 ms ping time during almost an hour with only 2-3 spikes to 300 ms. That is fine as crossing the pond often adds about 100 ms.
73, Palle, OZ1RH.