Hello. I am sorry to hear that Morgan is having some trouble. My name is ***** ***** I have been a veterinary nurse for 27 years. I would be happy to help.
No it would not be safe to give this medications. Acetaminophen while it can be used in dogs has to be dosed very carefully and can quickly reach toxic levels and phenylephrine is not used in dogs and considered toxic in any dose. Here is additional information on phenylephrine toxicity in dogs Link
Benadryl can be helpful if you have not tried that. This is dosed at 1-2 mgs per pound of body weight 2-3 times per day.
Claritin is another medication that can help NOT Claritin D . Here is information on dosing LINK
Your vet can also prescribe a medications called Atopica which works great for itching due to allergies.
Licking the feet can be due to environmental allergies but it can also be associated with food allergies. The only way to know for sure would be to have allergy testing done. One test we do in our office is called the VARL test. LINK
If Morgan is not on an allergy based food then trying a food change may help. You would want to pick a food that is grain free and have a novel single protein source such as rabbit, duck or kangaroo. Check the ingredients as many foods have more then one protein source regardless of what it may say on the bag. Natural Ba***** *****D line is a good food that you can get at a local pet store.
I hope this helps give you some direction. Please reply back if you have additional questions and I will be happy to continue. If you have no additional questions please take a few moments to provide a rating as this is the only way I am compensated by just answer for assisting you today.