Q.Regarding tangelo fruit
Our dwarf tangelo produces fruit, but when picked (it looks properly ripe), the interior flesh is rather pithy mixed with pale orange meat. Fairly inedible. What is the problem? Is the fruit too long on the tree, and should it be picked earlier? Had a dwarf Trovita Orange produce similar inedible fruit last year, but this year it is just fine.

Many factors can effect the fruit on a citrus tree.
Weather, temperatures, moisture, pollination.
Some things you can control, some you can't.
Here are a few links to help you pinpoint the issue with your Tangelo.
https://www.gardeningknowhow.com/ornamental/flowers/fgen/harvesting-garden-seeds.htm