I have many of the same symptoms that you describe. I thought I might share somethings that have been working for me. I take fenben twice a month 5mgs/kg 2x daily for 5 days, starting 2 days before the full moon and new moon. On the off days I take ivermectin, skipping a day every 3 days if I feel like I can.
What has really helped my skin symptoms has been topically applying natural and rx antiparasitics. I add thyme oil to my shampoo and leave on my scalp for at least 10 minutes while showering (stings a little the first few times)I've even added a few drops to my body oil and lotions. Use sparingly or start slowly. It does sting a little but it work. Really massage it in your skin well. Then always after massaging your body, wash your hands and under your nails well using a nail brush then treat them the same as your body because I found they will find hiding spots there and your hands will be a mess. Focus on your feet and problem areas. Be consistent with this.
I use topical ivermectin too. Not the paste though as I find that it does not penetrate non-mucous membrane areas on skin. I buy the duramectin blue pour-on kind. It really help with crawling and movements. You may also look into using dmso before the topicals but do your research and be careful with dosing as topical ivermectin does get into your bloodstream so make sure you're taking less by mouth if your applying topically. I started out diluting it and now I use it straight up. I dont always apply to my entire body unless the symptoms are really bad. I also apply it to my hair. Not just the scalp, my actual hair strands and that was literally life changing as whatever this is, seems to travel through the hairshafts. Bizarre!
I also use lugol's iodine topically on problem areas and it seems to help. I think it somehow weakens the cysts/nests. So pay attention to how the areas feel after applying and treat with other antiparasitics as needed. I put a few drops in my drinking water daily as well but you might want to research that more as I'm not an expert and wouldn't want to give you advice that could harm you or disrupt your hormones.
Also, oil pulling with coconut and 2 drops of oregano oil daily along with very good oral hygiene is important. I have made saline nasal rinses with a drop or 2 or lugol's part of this oral routine. Oh and dont forget about your ears. Inside and out. Find what works and stick to it.
Clothing and bedding I have found to harbor these things and should be treated as well. I wash everything on hot with a good detergent and borax and I add diluted permethrin to the rinse cycle (fabric softener input container) This has also been a huge help. When I go without doing this, my symptoms get worse. Change bedding often. I do every 3 days but I may be going a little overboard. Try to vacuum everyday or every other day and sweep and mop often. I have found that pinesol works well on floors. I understand in your condition keeping up with this is hard but I think these things can survive in the environment so its important to do this as best as you can and a little exercise is always good. Go at your own pace. It also makes you feel a little less helpless. I use a swiffer and just empty the old bottles and refill with the diluted pinesol. Makes the job so much easier.
I'm not 100% sure but I dont think you should be taking 2 bendizoles at the same time. If you find that they both work for separate symptoms, maybe try swapping back and forth during different times of the month until you find the right pattern. You have to be careful of your liver and kidneys. Which I worry could be the cause of your back pain. Be careful, and if possible try to get in to see your doctor for some routine bloodwork to check your liver enzymes and BUN etc.
Sharkman will probably be of more help with the exact dosing and stuff.
Always protect and monitor your organs while using anti parasitics.
Also, Matt3k has a lot of good info on supplements and other additions to your regimen. Maybe you're missing something essential. Maybe try reaching out.
Best of luck to you. Keep fighting!