The Visa Waiver program allows three month visits. So, you could be together for a total of six months each year.
No worrying about insomnia does not do the damage, the sleep deflict accompanied by it does. However worrying about insomnia can cause what is know as a vicious cycle which basically is the stress cause by worrying about insomnia can cause stress which is a cause for insomnia. Having Insomnia>Sleep Deflict> Worrying about Insomnia> Having Stress> Having Insomnia
Well, that depends on what you are worrying about and how much. If you are worrying about an upcoming test, study your hardest, and then whatever grade you get, you will know that you did your best and can be proud. If you're worried about a debt, and it's taking over your life, that is a problem, and then yes it is a sin. Hope I helped! <3