The client I'm working with found a good tax consultant who has been guiding us through the process on the tax side. It's been a huge help to have someone to monitor thresholds and explain "Nexus", etc... Not sure if that is an option for you, but it's allowed us to move forward with better peace of mind regarding taxes.
It's a tough topic to navigate, unfortunately.
It's strange that the VAT tax wouldn't attach on to future recurring payments for your members. It seems that should automatically be added to future charges as soon as you implement it.