It's time to move on from the T*i line of Canon cameras. I started out shooting on a T2i, and I loved it, but I can't go back to it. There are too many new, or used options out there, that give better results. I really love the quality of images from the Panasonic GH4 and the G7x. Canon is focused on the photography crowd at this end of the market.
With the bad luck in purchasing used, I'm going to suggest something new. B & H has had some great promotions on the Panasonic line recently. I would have suggested the G85 but that sale just ended. They currently have the G7 for sale with two lenses and a $50 gift certificate for $697 and a three year warranty. I'm really impressed with the video quality of this camera. If you can wait, the G85 sale may come up again. It was the same price withe the same lenses but with a $100 gift certificate. Here is the link to the current G7 sale. I am not affiliated with B & H at all, just pointing out a bargain. https://www.bhphotovideo.com/c/search?Ntt=g7&N=0&InitialSearch=yes&sts=m...
I had been thinking about the Sony a6300 as well but have been rethinking that as I have heard about overheating issues after 29 minutes of shooting. many are reporting the camera shuts down. Also battery life isn't as good as on a DSLR.
Sure, adding lights would be the best solution, but he mentioned he's using this camera to shoot events. A low light camera would be the best for this type of subject.
Most weddings have their audio sent down to a mixing board. If you attach a digital recorder to it with an XLR you will have the best audio without annoying the bride and groom with lavaliers.
Hey! Ho! Red Shark posted this article last month on how to build a Resolve system for $500 bucks! http://www.redsharknews.com/post/item/2815-building-a-resolve-12-system-...$500