How to practice mindfulness effectively?

[Reductor]

1) Is this normal? Is it progress?

The leaning over feeling happens to me, and I do believe that it results from not having the body tensions settled or the body tension being uneven.

As for the breathing fear: that's normal. Don't worry about the breath, let it go as it will. Unless you have a pre-existing condition that just happens to flare up while you're on your seat you will not die while meditating. Meditation will not kill you, even if the breath seems to have disappeared.

2) Should I actively strive to make my breath more refined, quiet, and short?

Again, don't try to regulate the breath... although if it is really uncomfortable at the start then take a few deep breaths, blow out your lungs and relax the tensions around the breath. Then begin.

When you're concentration improves and you really find your mind digging into the breath, the breath will become more refined on its own but you'll still have it steadily in view.

3) Should I worry about the shortness of breath?

No.

[Zom]

I am able to meditate multiple times a day for longer periods of time (samatha variant of anapanasati). I'm also going to be moving to Portland, OR from rural Arkansas, which I find encouraging because my opportunities for group practice and teachings will be dramatically expanded. I'm also going to use the move to formally Take Refuge with a bhikkhu/teacher.

I think this is a common mistake that people start buddhist practice from meditation. They take the Noble Eightfold Path and turn it upside down.
They start practising 6th, 7th and 8th factors (or even one of them) instead of starting with the development of the 1st one... :cookoo:

Better than nothing, but still not right.