I m not as experienced as some, but will start the answers.
1. Many people start their sewing with a "starter piece," a small piece of fabric...like 2 or 3 inches square. They sew on that and then sew onto their "real fabric" ...sort of meeting the edges and then just clip. Me, I just start at the edge of the fabric, holding on to the top thread, to keep it out of the way.
2. You don't need to backstitch when you are sewing pieces together. That should be one way to avoid the bunching up you are having.
3. Do you have a 1/4 inch foot attachment? That makes the 1/4 inch easier to do. Either method you mention works. I usually just try to get back to the 1/4 as quickly as I can.
4. I stop my bobbin thread just a shade inside the bobbin, so that there is no way it can rub against the bobbin case.
Welcome to the Quilting Board, by the way. You will probably get many different answers to your questions. That's okay. You can figure out what works best for you.
Dina