Your plan looks reasonable to me. There's not much to see in Varanasi itself besides the temple and the river, which you can easily do on Day 9 (early morning). It looks like you might even have time to hire a car+driver and see the Sanchi Stupa (historical Buddhist buildings) in the latter half of Day 8. I don't think there are direct flights from Varanasi to Pune. My guess is that you have found the best one possible.

PS: Are you the frugaltravelguy? If so, I love your blog. Thanks for all the tips and advice!