oh hun I am so sorry you have lost so many pigs in such a short space of time, but it happens it happend to me and Debbie ( furryfriends) at the begining of the year, all you can do is hoover the spiders out ( I dont think they are killing them) and use something quite strong and for animal treatments I use trigene it kills fungas spores viruses etc
and try not blame yourself, as for being paralised that happens when they have a low calcium level if she wasn't so far gone you could have tried giving her osteocare a calcium and vitamin medication , which would ahev reversed the paralasis but she sounds as if it was a bad paralasis, but for next time in case it happens again,
all you can do hun is make sure you are sticking tot he rules keeping them fed watered dry and warm/cool and I know you have done that so its down to nature as already said it could be inbreeding and thats something you might not know about, dont dont blame yourself