Regarding the observance of Lord Caitanya's Advent Day. Fasting should be continued up to evening, then you may have food like on Ekadasi, fruits, milk, etc. On the next day you may observe festival.
Regarding the observance of Lord Caitanya's Advent Day: No, there is no need for any other devotional songs or chants; simply chant Hare Krishna, with Kirtana or beads, and sing the prayer "Sri Krishna Caitanya Prabhu Nityananda, Sri Advaita Gadadhara, SriVasadi, Gaura Bhaktavrinda." You can also chant the prayer you asked about. This was spoken by Lord Nityananda while He was preaching in the town. He was addressing the people: "My dear brothers, you simply worship Lord Caitanya; talk of Lord Caitanya; speak Lord Caitanya's Name, so anyone who does so, he is my life and soul." Thus spoke Lord Nityananda. So far the reading is concerned, you may read any one of the books you have mentioned—Introduction to Srimad-Bhagavatam, Professor Sanyal's book, Srila Bhaktivinode's book Sri Caitanya Mahaprabhu Life and Precepts, or English translation of Sri Sri Caitanya Caritamrta. Best thing is to take any one of the above mentioned books and finish it, from beginning to end. You can do that with Srila Bhaktivinode's book, that would be very nice.
At the meeting everyone should try to speak something on Caitanya Mahaprabhu's life, teachings, and philosophy. You can take quotations from the above mentioned books, and have discussions. Fasting should be continued up to evening, then you may have food like on Ekadasi, fruits, milk, etc. On the next day you may observe festival.