Will the Friday preacher be rewarded for arriving early to it if he is unable to do so because of the sermon, and is there any specific virtue mentioned for the Friday preacher?

The virtue of arriving early for the Friday prayer is for the congregant (ma'mum), not for the Imam. The Prophet, peace and blessings be upon him, used to go out for the Friday prayer immediately after the sun's decline (zawal), and so did the Imams.

Following the example of the Prophet, peace and blessings be upon him, is more fitting and better. The Imam and preacher will be rewarded for his righteous intention, and his work in teaching people goodness carries a great reward; for he is among the best of the Ummah, those who are Imams to be emulated. He will also receive the reward of everyone who is guided by his words or actions.