A partial glossectomy does not constitute 50% resection. However, as the tongue is excised, additional material may have to be resected as well to achieve "clear boundaries". So a partial could become a hemi during surgery.

Was the neck dissection radical or partial?

If the lymph nodes are involved the cancer has metastasized from the original site and I believe that places your husband at Stage 3. (Don't get caught up in the numbers.)

The PET scan will show if any there has been any additional tumor growth outside of the head and neck areas and also better / more accurately locate the known tumors.

Regarding your questions about communication after reconstructive surgery - Your husbands other health issues combined with the course of action for the oral cancer, (resection / reconstruction / possible radiation and or chemo), will have a definite adverse impact on oral communication. Ipads or cell smart phones are an excellent way to communicate non-verbally.