I did not see that you have tried Doxycycline. This Antibiotic kills the symbiotic bacteria that have evolved within roundworms and performs a critical step in embryogenesis for the worms. 3-6 wks of 200 mg Doxy daily (I used aquarium product from online auction site). Once the Wolbachia are eliminated, the worms are effectively sterile and cannot reproduce. It doesn't kill the worms in any way. Once sterilized, your meds could be much more effective in killing off the remaining adults and the Fenbendazole can work on the encysted ones. I have seen excellent results for disseminated stronglyoides with monthly Moxidectin and 5 days of FenBen monthly. I still can feel the occasional buzzing worm but definitely weaker and at most for only a few hours. I expect to be on these meds for Life due to the encysted bombs laid everywhere in me.
Be aware that Doxy can cause photosensitivity to sunshine which was A REAL problem for me. But find a way.... Good luck.