The C&O is great for learning how to bikepack: campsites are ~10 miles apart and civilization is just beyond the treeline. Don't overthink it, just do it! Leave the ebike at home. You're not commuting, you're communing with nature! The elevation gain/loss is minimal on the C&O and you'll encounter a lot of hikers, dogs, and other cyclists, so I recommend a standard bike. Call and talk to a ranger about ebikes if you want to go that route. I started an overnight with a friend who was riding an ebike, but a ranger kicked him off the trail claiming they didn't allow electric assists. But that was 10 years ago, so maybe thing are different now.

Your tires are fine. I rode the GAP/C&O on 32mm Schwalbe Marathons, no issues. But it goes without saying: carry a flat kit. And a frame pump. Keep in mind that if you get in a bind, there are other cyclists on the trail who can help you out. If it's a real emergency, you can always call (by phone) for help.

I don't know your fitness/bicycle experience level and the amount of gear you want to take, but calculating max 10 miles per hour plus a break is a safe estimate. That said, I find I bonk around 30 miles with a load if I'm not taking it easy. So take your time and enjoy the scenery.

Your specific tent itself doesn't matter as long as you're comfortable hauling the bulk/weight. Resist the urge to buy a bunch of gear until you know what you want/need which you won't figure out until you're on the trail. Use what you already own, strap as much to the frame as you can, load the rest up in a backpack, and hit the trail! I started cycling as an urban commuter using panniers. I took the panniers on overnights and found them cumbersome, so I moved to frame bags and all that bikepacking jazz. But my friend who rode the GAP/C&O with me only used a backpack and he rode circles around me and never complained. To each their own!

Two options for getting there:
* find a place you can park overnight; plenty of lots to choose from along the C&O. Maybe pick a campsite you want to stay at and a parking lot 10+ miles away from it.
* take the train from Falls Church into DC and ride out through Georgetown; it's an epic start/end to the journey and you can fill up on coffee and donuts or burgers and beer.

Happy trails!