I would take the lane there. I do that coming up to a 4 way stop. That way i have a legal order behind cars. As I ride througj an intersection i go back to the right

This.

The only time I'll "take advantage" of a car as a shield is at a four-way stop sign intersection with a car proceeding straight (without question) in the same direction I'm going. I don't run stop signs when there is traffic, but also don't prefer to stop, unclip and put my foot down. So I'll slow, and when the car proceeds through the four-way, I'll go at the same time.

I need to exercise caution in such case, too (when passing a stopping/stopped bus on its left): For one, to make sure to watch for cars coming from behind, some of which do not slow down; also, there is a small chance the bus may not stop long after all (no/few passengers getting on) and could quickly leave the bus-stop while I have not completely passed it.

No, it's not odd at all. If you are close behind the bus, take advantage of the fact that the driver behind you is not likely to tailgate the bus. Occupy the space behind the bus that he is not likely to occupy. This gives you room to change your position within the lane. Do this quickly, because tailgating has the hazard of the bus stopping quickly. If you rear-end the bus, it's your fault. Then you can fall back to a safe following distance, and you have now created space between the bus ahead of you and the vehicle behind you, and you are in the position you need to be in.

You can move left and right in a lane as long as it doesn't cut anyone off. You may want to signal it. I make most of my signals with my head rather than my hands. I look back twice. This seems to be a really good way of getting drivers' attentions.

You definitely must start looking ahead for oncoming vehicles turning left in front of you. Right hooks and left hooks are the two biggest causes of car-bike collisions where the car driver is at fault. They are far greater in risk than rear-end collisions. Rear-end collisions are rare in the daylight. Ostensibly, drivers are looking straight ahead most of the time. With the increased use of cell phones while driving, this is becoming untrue, but I hope the trend reverses. If we can't assume drivers are looking through their windshields, what can we safely assume about them?

The first is the main worry. The second isn't a big risk, IMO - assuming you aren't pootling along at 8 mph, you should be well clear of the bus no mater how short the stop is.

Not a good idea, especially through an intersection. Think about when you wait in the left turn lane in your car, and a bus comes the other way, going straight. What side of the bus do you see? The left (driver) side. If someone is on a bike behind the bus, towards the left side of the lane, you can easily see him/her from your car. If the cyclist is behind the rear right corner of the bus, you won't know the cyclist is there until much later, possibly even not until after you have started your left turn across oncoming traffic lanes.

Yes, a bicyclist tucked up behind a bus in the right rear corner can't be seen. OTOH- he can't be hit by a left turning vehicle unless it has warp drive. Even if the driver tries by timing his turn to just clear the corner, and taking it in as tight a radius as possible, he can't come to within 5-10 feet of the right rear corner. Since the bus and bike are both also moving, that means they'll have left that position anyway.

However, it's important to stay tucked into the protective corner, and not hang back far enough where you might be hit.