Student or Learner
1. If I want to say 'Sorry if I were able to disturb you', can I just say 'Sorry for disturbing you.'
2. Is 'disturbing' here a verb?
3. Can I use it though it has something to do with the present?
"Sorry for disturbing you" is absolutely okay. It can be used to refer to something in the past or something going on right now. You can also say "Sorry to disturb you."
Your original isn't natural at all. Aside from not being right grammatically, it sounds like you were trying to disturb him.