I & a few others who use hot, use the anologue pump controllers from Gardiners with the external D/E control numpty.
Its easy to set the flow and D/E which will alter with how hot/cold the water is.
This will also help with connectors popping off because of pressure build up.
As for the hose reel internal bard fitting, is this on your new reel, try doubling up the "eared " hose connectors