Is This Permitted?

Shalom aleichem Rabbi Lauffer. Thank you for answering my last question. Would it be permitted to brush one’s teeth with toothpaste after sunrise but before davening shacharis? Thanks.

Is it permitted to trim tzitzit strings on tallit katan if they are very long (e.g. knee length) and get in the way? If so, by how much?

I know you people have a commandment not to commit murder. And you are not supposed to violate it even to save a life. Then what permits killing in self defense?

If someone were to theoretically take a nazarite vow, could they be allowed to trim their moustache if it made simple tasks such as eating food less troublesome? For the vow it is written to not cut a hair on the head so would this include facial hair, eyebrows, and even nose hairs?

My neighbor says he likes my sukkah so much, he has offered to trade his with me for mine. He showed me his and I actually like his better than mine because it is more spacious. He likes the material mine is made of. I am not badly attached to my sukkah. I got it several years ago from someone who was giving it away. I actually like this trade. Does Halacha permit this? One of my concerns is that either of us could be violating the tenth commandment by coveting a neighbor’s property, even if we both agree to this trade.

My father-in-law died. I was never close to him, and he was sick in a nursing home for many years. My husband is sitting shiva now. I have tickets to a concert. He says he is okay with me going. Is it permitted for me to go to the concert with a friend while my husband is sitting shiva?

I am on an airplane now as I’m writing this. I got up to use the lavatory and spent a while there. When I returned, my elderly mother I am traveling with fell asleep with her head on my seat. It is a full flight and there is nowhere else to sit. I had no choice but to wake her up out of a deep sleep. She was startled but is not angry about it now. She didn’t grant me permission in advance to wake her up. Did I do the right thing?

I made a new friend who has exactly the same given name as my father. Is there any problem with me calling my friend by his name?