Let's dissect your first draft, okay? Good for you to try this out here. This is a good learning tool.
WAH- I understand why you are asking me to update the timeshare login in order to do your own research. [You don't understand nor pretend to. I'd suggest you drop this line.]I am happy to do that assuming you ["assuming you" is asking for fireworks because you essentially implied to H that he cannot be trusted to do the right thing]could do the same for me with regards to the hotel rewards account. I ask that you not book or use this 'assets' without us jointly agreeing [this comes off as controlling...you cannot control what H does or does not do]to it first as I would give you the same consideration with the hotel points.
~~~~~~~~~~~~~~~~~~~~~~~~~~ You need to re-work it or start all over with a different response. You would want to reduce "I"s here. Maybe start with subject or noun. Using "I"s just weakens your position further. You will need to use the language from power.
Speaking of which, I'd highly recommend that women here buy this fabulous book:
How To Say It for Women: Communicating with Confidence and Power Using the Language of Success by Phyllis Mindell
