I wouldn't use these two in your hmm.. letter
- And I feel like I could look into your eyes for hours and not get tired == Я чувствую, что могу смотреть тебе в глаза часами и не почувствовать даже толики усталости
- When we talk, I feel completely at peace and I don't want to stop == Когда мы разговариваем, я чувствую умиротворение и не хочу останавливаться ни на миг

That translation is perfect but we don't speak this way it will look unnatural

Also keep in mind that it can only be used to talk to a girl. I mean first of all it's written in feminine gender and secondly if the lady is in middle age I wouldn't start talking "ты" it will be inappropriate


Hope my post doesn't look too negative