hmm, force feeding a tortoise. To be honest, the best way to do this is reverse psychology and get the tort to want to eat on it's own. Optimum husbandry is a must, and warm temperatures are a part of this. Whatever initiated the pneumonia must be corrected. Weigh the tort regularly to monitor loss of mass.
Optimally, actual force feeding for a tortoise is a vegetable slurry, worked into the mouth with a syringe and gently administered allowing the tort to swallow. The risks are inhalation which will complicate the pneumonia, and stress, which will complicate everything. If corrected husbandry and medical treatment will not entice an appetite, then a surgically placed feeding tube needs to be decided upon. They work really well, and also make it easier to administer medications. Go to the box turtle forum for an account of "Chip" who is having this done right now.
The pinworms are not an immediate concern, if one at all, unless they are in sufficient numbers as to be causing clinical signs. You would be seeing a soft runny, stool that is not related to inappropriate diet.
Ian