Once you switch to the SmartSense Open/Close sensor you are good. Leaving the DTH by tomaasaxerot wont hurt anything. I would leave it there for now.
I can’t remember which thread was it but someone else had trouble adding a few of the sensors, he reported back that eventually he was able to add them after adding zigbee repeaters to make his mesh stronger/more robust. From what I understand any zigbee device that plugs directly to outlet (doesn’t use batteries) will serve as a zigbee repeater.
My digitaldiscount https://www.mydigitaldiscount.com/centralite-3-home-lighting-lamp-dimmable-control-module-for-samsung-smartthings-and-other-smart-hubs-with-zigbee-wireless-model-3100/
has Lamp zigbee plugs that you can use or maybe buy the Lowes Iris appliance v2 Plug as that one is also a zwave repeater on top of being a zigbee repeater. Maybe buy two https://www.lowes.com/pd/Iris-120-Volt-White-Smart-Plug-Works-with-Amazon-Alexa/999925330 and use $15 off $75 coupon. Or wait for a Lowes promo on them to get price lower.