Don't let anyone tell you that either Nikon or Canon is better than the other. They both make excellent cameras that will be able to give you great results. I would go to a camera shop that sells multiple brands (Canon, Nikon, Sony, Panasonic/Lumix, etc.) and give them a try to see what you think. Ask about lens options to get an idea of the ecosystem. Also if you have friends with camera like the kind you are interested, talk to them and see what they think. Play around with their cameras.

By those definitions, I would think "Semi-Pro" would be between "Pro" and "Amateur".

I would define "professional photographer" simply as someone who got paid for their photos. Even if you only get paid for one photo, you are (or at least, were) a professional.

Leave the percentages for those trying to define if they are a "Full-Time or Part-Time professional photographer"

The SanDisk SD cards that came bundled with my 70D were not fast enough for recording video. I kept getting a "Movie recording has stopped automatically" message after a minute or so. I replaced the cards with SanDisk "Extreme" SD cards (with a higher MB/s rating) and that solved the issue.

If you take one photo at a time, I don't think a "better" SD card would matter in terms of storing an image as long as it is a quality/reliable card. But if you do a lot of burst photos/video then getting those files to the card in time could be an issue depending on your camera and settings.

I use an OP/TECH USA "Classic Strap" but I changed the connector to an XL "Pro Loop Connector"

Nice affordable plain black strap (not advertising the camera or strap company) and very comfortable. It's made in the USA, I've had the strap for about 4 years and have not had any problems with it. Just changed to the loop connector recently from the more traditional "3/8" webbing connectors"(the same kind the factory strap uses) to make it look cleaner.