Is it okay to get distracted while mindfully meditating?

Don't press the trumpet into your lips hard. Also, practice at home and your lips will build an embouchure memory, and it will be easier to play.

Actually, the purpose of meditation is not to think at all! While you are awake, our thoughts rise and fall continuously. Often, uncontrollable thought flows distract us from being present...

You're not required to close your eyes, but it is respectful towards your god/gods to do so. It is also respectful to the leaders who guide you, because then they...

Yes. If you allow yourself to sit comfortably while you're meditating, you can get to a deeper place than if you're worried about your posture.

If you're just starting, you can easily meditate sitting in a chair. If you want to try something more advanced, you can get into the lotus position.

Reproducible chest pain (pain only by pressing on the chest) is usually not angina but rather musculoskeletal. Such pain should be further discussed with your physician to further differentiate.

If you keep getting distracted by other people being noisy, try wearing headphones to help keep you focused.

Of course your dog isn't dumb. Perhaps boredom is the issue here. Some dogs are just low-key and not easily distracted.