I think your post illustrates very clearly the point that has been made recently about how easily we can get into a mode of assuming bad intentions from our spouses whether they are actually there or not. As you clearly stated, your H assumed sinister motivations to your money management, and that escalated into a general fight about the relationship.
I personally think the best tack would be for you to directly, calmly address the money issue, separate from anything else. If he tries to escalate or make ludicrous assumptions, call him on it, and don't back down.
I would be leary about the letter. Although the words you speak may be true, well-spoken, and clear, these sorts of disputes are rarely solved by letter exchange, in fact, they generally just tend to escalate. When you write a letter, there is no give and take, no body language to soften the statement, etc. It is my prediction (for what it is worth) that your H will read that letter and become even more angry. It doesn't matter if he should or not, that is just typically what happens. Depending on the MO of your H, you might get a nasty letter back.
I think it would be best to take care of the money issue first, then LATER bring up the general respect, good communication issue. Just my 2 cents.
Chrome
"Recollect me darlin, raise me to your lips, two undernourished egos, four rotating hips"
