It's my understanding that a fiction writer has pretty much free reign
dealing with historical personages, much more so than trying to use
copyrighted fictional characters. This is true if you're drawing from a
variety of sources in the public record--if it's obvious you're dramatizing
one bio or study, than that author might be interested in a percentage.
Images are a trickier matter--they can indeed be copyrighted and protected.
But a family can't claim protection of any family member, although they
might want to try. If so, probably the better--any legal action would serve
more as promotion than threat.

I think of the lawsuit a few years ago by the writers of Holy Blood, Holy
Grail who sued Dan Brown thinking their book was the primary source for his
novel. They rightly lost--but this simply means if you have a cash cow,
someone will want a piece of the pie if they can get it. For Pound, there
are trial transcripts that are public, I presume his broadcasts are public
domain, but his poetry is likely protected. Ask your potential publisher.
Some are queasier than others. If film rights are involved, they might want
to ensure there's no storms on the horizon.

From personal experience, I'd add it's often troublesome to try to deal with
families of famous folks as they often want more creative control than any
creative project can endure. Don't ask, don't tell--in this case, that adage
might fit the situation.
Good luck!