My family i live with goes around maskless but i wear a kf95 at all times and try limiting contact with them regardless of symptoms (some always have runny noses or cough even before the pandemic). is this reasonable? i'm high risk?

Unless you have a chronic medical condition like rheumatoid arthritis, immune deficiency, diabetes or similar problem your risk from covid approaches zero. Mask if you wish, but it has marginal benefit now if it ever did in the past. It is good to mask if you have a runny nose or cold symptoms to prevent its spread to others. Otherwise, I consider it of little value.

Wearing a mask will protect you from respiratory pathogens as most of the pathogens are carried by droplets. Wearing a mask will not do any harm. On balance, you are far better off wearing a mask than not wearing one. Wish you good health!

You claim to be high risk, if that is the case, family or any known, or unknown people can cause an infection. Wearing a mask is safe, but you should know your families history, did they get the vaccine and boosters, and did you? We are all still at risk, even with the vaccine and boosters.