What's your question? Ask

Yes, you do. But you will want to wait to trim it for a year or so until it has established itself.

It would be better to prune in late spring. This article will help: https://www.gardeningknowhow.com/ornamental/shrubs/pussy-willow/how-prune-pussy-willows.htm

Typically if a plant's flower seems faded, it is due to a lack of nutrients. I would fertilize the plant with a balanced fertilizer. If you can, get the soil tested as well to see if there are any micro-nutrients lacking.

Have you pruned it? It only blooms on new growth, and when you prune, you cut off the new growth. This article will provide additional info: https://www.gardeningknowhow.com/ornamental/shrubs/pussy-willow/how-prune-pussy-willows.htm

It sounds like you have a pest problem...and not the ants. Most likely your plant is infested with aphids or scale, both of which secrete honeydew. It is the honeydew that the ants are attracted to, so getting rid of the pest in questions will eventually get rid of the ants. There could also be a fungal issue as a result of the insects. I would receommend treating the pussy willow with neem oil, which will take care of any insect pests as well as fungus. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

Here are some links to articles that you may find useful on this subject.

https://www.gardeningknowhow.com/ornamental/shrubs/pussy-willow/how-prune-pussy-willows.htm

The pussy willow bush may have gotten a fungus and sometimes they are not easy to see. I recommend spraying the entire bush down well with a good fungicide. My own pussy willow bush seems to go through various stages of health after it too was broken down by a late heavy wet snow storm. I keep it sprayed with a fungicide at least twice a year and also give it a tree food spike or two every year. It is big enough that I give it two tree food spikes and I imagine yours is too at 10 years old now. Mine is around 20 years old.