1 I heard in Upanyasam that dried Tulasi leaves can be used for Thiruvaradhanam; similarly, can we use slightly withered Tulasi which is homegrown? 2 Who should do the last rites for those who do not have male progenies (Sons and grandsons)? 3 In Aranya Kanda (3.48.8) Ravana tells Sita Piratti that Sun performs his duties out of fear of Ravana; as per Yuddha Kanda Lord Rama killed Ravana after worshipping sun through reciting Aditya Hridaya. What is our Acarya’s’ explanation on this?

Dried Tulasi leaves can be used but not plucking of the purple/yellowish or dried leaves.
Husband-wife can perform, followed by close relatives or brothers can do. There is an order for this depending on who the kartha is. Books like Acara Sangraham provide details on the order of Kartha-s. If the woman is present, darbha grass can be obtained from them to perform the rituals.
Aditya does not obtain power vested by Ravana. It is Emperuman who grants him the strength and by its power, He killed Ravana like how He destroyed the clan of demons through the monkey army.
Notes:
When Emperuman recited Aditya Hrudaya, He worshipped the inner Lord Narayana.