Re: Legal advise
It's because of his transferring money from a business account to a personal account that I think you need somebody like an accountant to get involved. The fact that he did it does not mean that he had any right to do it. It wasn't necessarily wrong either, so long as everything is recorded and traceable.
Similarly, any money earned during the period of the partnership belongs to both of you, and it doesn't matter greatly if the payment was made in his name, the business name, or even a cash payment.
It looks to me as if there is a lack of trust between you. That's yet another reason to get a professional involved in helping you to unscramble the situation.
On the assumption that your outline description is more-or-less fair, I think you almost certainly have some rights in this matter. You are right to have some hope. But, for your own peace of mind, don't build too much on it. If there is bad feeling between you, and if he is determined, he can make it very difficult for you to get your due. Don't go spending a few grand this week in the expectation that you will have lumps of money coming to you next week.
[As a negotiating tactic, it might be worth drawing to your former partner's attention that a lawsuit alleging fraud can be very damaging to a courier business. It might encourage him to reach a settlement with you in preference to going to court.]