Drive shaft boot torn

So lately ive been feeling a thump when i come to a stop and when i accelerate from a stop. It sometimes does it but it does it enough to where i notice. Everything underneath looks good. I was lucky and i have fully sealed u joints. The only thing is the heat shield that covers the gas tank was bent out and cut this boot.
Is this likely the issue causing the thumping?
Is there supposed to be grease in this boot?
Is there a replacement?

 

Yes. That could be your noise
It will have some grease but not much, it’s a dust boot.

they are replacable

 

When you separate the shaft to replace the boot, you want to add grease to the splines of the slip joint covered by that boot after you clean any grime and such out.

There is a special slip joint grease that's fortified with Teflon/PTFE but i've always just used moly grease. You want to be liberal with the grease but not pack the joint so full that it'll hydrolock itself when fully inserted.

Also as you've noticed, the truck is still drivable but, I would replace the boot sooner rather than later before so much grime gets in there that it wears the slip joint.