What is the best way to get from Sevilla to Tangiers and how long does it take? Also I've heard there's a 6am bus out of Sevilla to Algeciras and then a bus to Tarifa? From Tangiers, again, what is the recommended way to travel to Granada?
I cannot help with your ferry crossings, a simple google should find the companies. From Seville
http://www.tgcomes.es/horarios_33.htm You are correct for 0600 Monday to Friday - http://www.activagest.com/linesur/admin/horarios/sevilla.pdf If you arrive back in Algeciras - my recommendation, train to Granada, three times a day on a scenic route - www.renfe.com The alterantive is bus - www.alsa.es
An alternative bus from Algeciras to Granada is Avanza.
http://www.venta.avanzabus.com/