I'm so sorry to hear that poor Sentry is feeling unwell. It sounds like you have the situation in hand though. I hope nothing is wrong with him other than worms.
I buy dog wormer (WormOut) with active ingredient praziquantel (in addition to one of the older
benzimidazole drugs like panacur) from PetsMegastore in Australia and treat several times a year as a matter of course. That combination safely kills hookworms, roundworms, whipworms, tapeworms, and hydatid tapeworms..basically
everything. Internal parasites are nasty and pervasive little fiends.
Hope Sentry feels better.