Chickens will eat turkey feed fine, might not lay the best on it though

I'd just keep them on the layers pellets and maybe put some wheat or other grain out, my turkeys would take wheat and maize before their proper turkey pellets.
Same wormer will be fine for the turkey, do you know what age he is?
mine are just starting to mate at 6 months so he might well be on the lookout for a lady Turkey

They can pick up blackhead from virtually anything, earthworms, wild bird droppings etc but if you are worming there shouldn't be a problem.
Some people keep turkeys with chickens for years without worming and never see it, some catch it straight away, its just your luck
