I live in Nashville, TN climate area 4A

My issue is my attic gets so hot in the summer months and my heat pump runs a lot but does not cool very well. This is a duplex home with each side having around 980 sq foot living space.
I’m not able to move this units to under the house. The attic when you stand up is about 4 feet at the peak of the house. For each side of the duplex I have a 2 ton Rheem unit (one 2 years old the other 1 year old) cooling 5 rooms (2bd, living, kitchen, broom). The overall attic ductwork is 17 years old. I have checked already for any air leaks and used the ductwork mud to seal the best I can. Whatever I do I don’t want to hurt the roof or shingles.

What can I does that would help make my heat pump work more efficient in the summer months?

Should I replace the ductwork does it get too old to work properly?

If I double insulate the ductwork would that help with blowing cooler air? If so how would I do that?

The attic currently has blown insulate that’s not the best and I was thinking about replacing it with the roll kind in between the joints and then criss cross a layer on top in a different directions.

Thanks for any help you can give.