MacBook Pro is a great choice. I have 3 backups of all my images on external hard drives. Two of them are stored at different off-site locations. I used to have only 2 backups, and both of those failed. The tech where I work was unable to get the files off the first one he tried but was successful with the second one (more than a year's files). That's why I now have 3 backups.
I agreed to this once (about 45 years ago). When I got there, there was no place set for me. I figured that was not the couple's fault, so I did stay and photograph the reception since I had already done the wedding.
According to some reviews I have seen, the Canon 16-35 f/4 lens is Canon's sharpest. It also has IS vibration reduction.
Are you judging sharpness in a raw file or a jpg converted in camera. All raw files need to be sharpened to get maximum sharpness. Sometimes jpgs do too. The equipment you are using has excellent reputations. I have the 400 and it is an outstanding lens. Have you tried shooting from a tripod? Monopod?
I always take at least 2 external drives and keep them in different places in case of some kind of disaster. Those images will probably be the only thing on your trip that are not replaceable.
One of the best Canon lenses for bird photography is the 400mm f/5.6. It is not IS but it focuses very quickly. The 300mm f/4 with 1.4 converter is another good choice. Both are relatively light weight (so hand-holdable). I'm sure there are third party lenses which are ok, but I don't have any experience with them.
Use whatever ISO you need to get sufficient shutter speed and lens aperture.
Nikon will not repair grey market items. I once dropped a 600 f/4 Nikon, with body attached, and Nikon would not repair the lens because it was grey market. They would also not sell parts to an independent repair shop. They wanted the serial number, and, because it was grey market, would not sell the parts. I switched to Canon.
Buy a good tripod that is strong enough for any (un)anticipated needs, unless you want to end up buying 3-4 tripods over the years. The tripod is not the place to skimp.
Most of the ones I see are knock-offs of the Wimberley. In my opinion, the Wimberly is the best.
Hard disk is not always reliable. Just recently I had two copies of all my images (several hundred thousand) stored on 4 drives in two locations. The two drives that had all my 2007 files both failed. I took one to the tech guy I know and he couldn't recover anything from it. When I took him the second one, he was able to recover all 1 TB of the images. "Whew". I now have 3 copies of everything, stored in 3 different locations. Not as trusting as I once was.
Think of the rule of thirds as a suggestion, not a "rule." It is not appropriate for all images.
The mistake I made (only once) is to not anticipate future needs, and buy a tripod that is not sturdy enough. With your long lens you need a substantial tripod. You can spend money on a cheap one now and realize you need to replace it before long. Get one that is substantial, Gitzo or Really Right Stuff, if you can afford it. The RRS B55 ball head is the best I have seen. If you plan to follow focus on birds with your tripod, the Wimberley is excellent. I have a Gitzo 5000 series and 3200 series (carbon fiber) that work well with a 600mm f/4. I have an Induro CF 300 series that I use only for landscape with small lenses. My advice is: buy enough tripod for any possible future needs. Gitzo and RRS will have them that extend to the height you need. Gitzo is somewhat cheaper.
I use Canon equipment, and only use live view when on a tripod (almost all my images are on tripod) and use live view only to get critical focus. It is especially helpful for macro or when I want to isolate the main subject by using a wide aperture.
I use zooms covering 16-200mm for landscape, with an occasional 300mm. I use mostly 600mm for wildlife.