We are glad you are learning a skill like truing a wheel! It is important to keep the concept of the wheel as a system in your head as you work. It looks like I'll be the first one to say it, and it's potentially premature, but 79pmooney hinted at it: The wheel was extremely likely sold in a round and true configuration, and something has changed to make it no longer true. More than half the time, that 'something' is damage to the system.

The spokes pulling to the opposite of the bump will do the majority of the work to true the wheel, but you'll want to spread the pulling around the rim like mpetry912 suggested. I second that you should 'pluck' the spokes like a guitar string and listen to how the tones change around the wheel to approximate how much tension each spoke is under. The goal would be to bring all the spokes on the same side of the hub to a similar tone. Since this is a rear wheel, the spokes on the side with the cogs should have a higher pitch, because they should be under a higher tension and thus have a higher pitch.

I didn't see an answer to your first question. My advice is that riding on a wheel that is out of true enough to rub the brake pads won't hurt much to get home or if you're in a pinch, but loose spokes only continue to loosen. The rim will fail once enough support is lost and you'll have a more expensive repair when that happens, so correct it sooner rather than later.