What's your question? Ask

I would consult a qualified arborist or tree professional to prune the tree.
Tree branch stubs should not be left on the tree.
http://www.savatree.com/sycamore-tree.html

You should cut them. This article discusses how: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-sucker-removal-and-tree-sucker-control.htm

Personally, I use wettable sulfur to control fungus issues. Rosemary oil, lavender oil, and garlic extract can help in many cases. This article will help:https://www.gardeningknowhow.com/ornamental/trees/sycamore/sycamore-tree-problems.htm

Yes ,this wood has many uses. This website will give you more information on the subject: http://www.wood-database.com/sycamore/

There may have been environmental issues with the flowering and seed formation of the tree.

There can be variations in the amount of seed pods formed each year and your tree will likely return to seed production next season.

You could check with your County Extension Office to see if other reports of lack of seeds have come in from your region.

They may be able to give you some help on weather effects on your tree.

Here is a link to help you locate your nearest office.

https://www.gardeningknowhow.com/extension-search/

These are very fast growing in most areas, even growing as much as six feet in a single year. They can live longer than 100 years in many cases, so they can tend to get very large. They can reach about 30 feet by that time in areas where it is invasive. and will reach anywhere from sixty to over 100 feet tall when fully mature.