@OP
Do 250 Merit vote also allocated in Random fashion? If you have added 15 people and having 250 plus earned merit then will it be random for 1 of 15 to get that vote?
Not following this DT topic now so now idea if Theymos added some more points after one week of inception.

Each user's number of "votes" in the last two criteria will be limited to floor(earned_merit / (10 or 250, depending on the criteria)). If you trust more people than your limit, then you will vote for the people to whom your vote will be the most useful, more-or-less.

I wasn't able to find either an optimal or low-error-approximate solution to this problem. My current algorithm is sub-optimal in general and could produce results uncomfortably far from the optimal solution, but the current data doesn't actually present a scenario where it matters: my current algorithm is optimal with the current data. Long-term, if I can't find an algorithm that I'm happy with, I could make the trust lists ordered as some have suggested.

When building your trust list, I tend to encourage people not to worry about little details like this, and instead just think about the system in broad strokes. If this results in poor outcomes, then that's a problem on my end.