I had a pony with pneumonia over 30 years ago. He got through it okay and I am sure veterinary medicine has improved immensely since then so keeping everything crossed there will be some positive news soon.
Only just read this - I'm so sorry for all you two have been through lately, you just don't deserve it (not that anyone ever does, but still). My thoughts are with you both, wishing Gem a speedy recovery and you the strength to get through another setback. Big hugs xxxx