To say "right now" you have a few options. Which one is most appropriate will vary with context.
You can use ちょうど今 to mean "just now [a moment ago]" as in 「ちょうど今電話が鳴りました」"The phone rang just now."
今すぐ is perhaps the opposite, used to describe actions that happen immediately after the utterance. Because of this it is often used for commands as in 「今すぐ宿題をしなさい!」"Do your homework right now." But it can also be used in declarative statements, such as 「今すぐ宿題をします。」"I'm going to do my homework right now.
In formal contexts, you will often hear the polite expression ただ今 (of which the ただいま meaning "I'm home" is a derivation). This is similar to 今すぐ in that it describes what will happen directly after the utterance. You will often hear it used in announcements in public places, such as「ただ今、電車がまいります。」"The train will arrive presently.
As for your question about a construction to describe being interrupted, you will often hear people use 「途中」which by itself means "in the middle of" or "on the way to." In your example sentences, it could be used as follows: 「テレビを見る途中で電話が鳴りました。」This does not however, convey the same degree of annoyance as the English word "interrupt."
I hope you find this helpful.