It is dead if it has no leaves, sawdust could be carpenter ants,

It has leaves. Might it be okay?

you can use poison.

I’ll look it up.

If you have never cut big limbs up in the air
now is not a time to learn. My tree cutter was thrown off the tree
on my last tree he cut, luckily he had a saftey harness on, a
branch came bach and hit the tree and shook it, he was hurt but
could of been dead.

I have never cut big limbs up in the air... Might it be affordable
to rent one of those lift vehicles, so I could reach the limbs where
they are more manageable?