If a retired Musi resides in the USA but receives a pension in Pakistan and contributes Hissa Amad from that pension in Pakistan, can those contributions be adjusted against the $300 minimum due in the USA within the Schedule C declaration?

No. The Pakistani hisaab is entirely separate from the USA hisaab. Donations made in Pakistan are reported to Sadr Anjuman through the Schedule C form. The minimum Hissa Amad contribution of $300 is still required in the USA, based on the minimum standard of sacrifice prescribed by Majlis Karpardaz for the Non Earning Musian in the USA, and must be declared to Wakalat Mal II, Tehreek-e-Jadid, via the Schedule C form in the USA.