I went the bottom route for Haato too, though I made an exception for Toru so I don't know the exact details, but for Shuu it took about seven times for him to change from sub to dom. Is Toru still a sub according to Fundashi after seven times?
I do think it's all down to numbers - so if Toru's a bottom to start with and you've had him bottom seven times, it may take a lot of topping to get him up there. One way to do it might be to take the initiative in foreplay but choose to bottom until you get him to top, then never take the initiative again... might work. I don't think not inviting him helps at all, sadly. I tried that with Shuu, and he never called me no matter how toppy he was.
Oh, but if you skip the foreplay you can choose your position directly - so you could just choose to be a submissive bottom for the first seven or so times and then see if that gets him to where you want him. I think that still affects the statistics.
Hope that helps! :)