Seems like you're using Enketo which does not support range-widget labels. Use ODK Collect instead. Maybe upcoming ODK Web Forms will also support range-widget labels.
Yes, absolutely! We are about to release a Central update that will make Web Forms the default for newly-created forms. Our current high-level priorities are to fix any issues that are brought up and to fill in remaining functionality gaps that may prevent users from switching. Because tick_labelset isn't in Enketo yet either, it's not at the top of our priority list but hearing that it would be valuable to you gives it a nudge so please keep the feedback coming.
Glad to hear! But no hustle - since we currently only run a Kobo server it might take a while so we can enjoy Web Forms. Also, because of some restructuring processes we do not really have a server admin to set up ODK central. If Kobo has no plans to ingrate Web Forms in a timely manner, we will switch to ODK anyway. So take your time - I'm grateful for you working on Web Forms. Enketo was/is nice, but has its flaws and limits.