I'm pretty sure that Options->Controller->Options allows you to specify what the up and down intervals are. (You'll have to uncheck "use one page for interval" and specify your own value)
Beside that, I would strongly recommend using ROMlister or a similar utility to cut down on the number of games you're scrolling through. It's probably still going to be a chore to scroll through 7000 titles regardless of the changes you make with MaLa. After removing clones, adult games and a few others, I'm down to a little over 2,500 on my list and I'm still trying to narrow that down some.