Hi JP and welcome - you came to the right place! So sorry for what you're going through. The NSD is rough at first but it gets better - it has completely changed my life.
A few things that helped me:
1. Low starch doesn't need to mean low carb. I also fell into ketosis, which is not harmful but I didnt like the way it felt...so I upped my carbs with low starch fruits (e.g. strawberries, kiwi, pineapple, ripe mango), honey, and occasional Cadbury milk chocolate. I eat about 130g of carbs each day but only 5g of starch.
2. When I lost too much weight I ate more fat to replace starch calories. I'm a big fan of coconut milk (eg. soups, smoothies) and choose fatty cuts of meat (thighs instead of breast, stew beef, etc.) We live in a fat-phobic world so this can be hard to accept but my cholesterol levels are no higher than when I ate starch.
3. After a few hard weeks I took the pressure off myself to figure it out by yesterday. NSD works (it's already working for you...that's why you can notice a worsening) but the first months are unpredictable as you figure out your own personal starch tolerance. You can spend every night on research but you'll still make mistakes, so focus on learning as you go. I noticed some improvement early on but it still took 3 months to perfect it and be consistently low/no pain.
Suspected USpA. HLA B27, xray, u/sound, blood tests all -ve. Ancient history of plantar fasciitis, SI joint pain, knee arthritis. Recent history of tendinitis, neck pain, debilitating finger pain and stiffness (especially mornings). No diagnosis, no meds.
2010 - stopped eating dairy
2012 - stopped eating wheat
2014 - stopped eating all grains
Jan 2017 - discovered NSD - 98% improvement in symptoms, continually amazed by my results, wish I'd found kickAS sooner