1. ALWAYS best to go with manual focus if you want full control over your shots. While autofocus is fine for some purposes, it's not always reliable and it won't do the focus pulls the way you'd like (9 times out of 10).
2. No, not really. One cinema lens would be many times the value of the T3i body, so from a price/quality standpoint it doesn't make a ton of sense. That said, if you're investing in glass then you're investing in glass! What are you thinking in terms of "Cinema Lenses"?
3. Yes, but make sure you know how much weight it can handle so you can figure out which lenses are right weight-wise. It might be worth investing in the Ronin-M as the payload (max camera weight) is higher and could handle heavier lenses. If you don't factor this in, you might have too heavy of a setup and render your gimbal useless.
Happy to answer any other questions you have. Hope this helps!!
Whatever you do, please don't use the drone during the ceremony! I can't imagine anything that could kill the mood more than a noisy drone hovering over the bride & groom while they say their vows, not to mention it'll mess up your audio as well. I've seen it done before, yikes...