Do you have any veterinary mucus thinning products in Canada? The UK brand name for it is bisolvon; it is prescription-only in the much more restrictive UK legislation.
Please also see whether a bowl of steaming water can help; if yes, please conduct half hour steaming /nebulising sessions. Ideally you add a little mild antiseptic to help tackle the infection from another angle.
I have been lucky to not have had to deal with any respiratory infections in my own adoptees for over a decade but other forum members may help you with practical nebulising tips. In a pinch, a steamed up shower with a warm and dry towel can help.
First Aid Kit: Easily available non-medication support products for an emergency
The third angle is support feeding. The need to breathe comes before the need to drink and only thirdly the need to eat, so support feeding is important to replace the lack in hay intake which makes over three quarters of the daily food intake and to also offer water to drink actively from a syringe during a feeding session. Support feeding babies is an extremely tricky process since the smallest bit of feed that gets into the lungs will cause pneumonia.
Here are our baby feeding tips that help you to prevent that:
Hand-rearing-and-support-feeding-orphans-and-tiny-babies
All About Syringe Feeding and Medicating Guinea Pigs with Videos and Pictures
I truly applaud your care and your will to help. Please be aware that it is very much a battle against the odds between the small weight and a not yet fully developed immune system. All you can do is try your best and make the little life count.