A battalion is traditionally made up of four to six companies of soldiers. Each company has around 1000 people. If you wanted to compare the dragons to maybe a modern tank, thats 31 tanks/dragons and would make up around 130-200 people depending on attachments as i doubt there wouldn't be infantry attached to said mounted units.A battalion might be different in numbers when you factor in dragons. Say if you weighed the fighting power of a dragon vs human.
We don't know that he is the only one kind to dragons, he said it's just very common to treat them like most people treated a horses when they were primarily a tool. Also as far as lvling up the guilds, dragons are essentially like humans and have diverse wants/needs but only OP can actually talk to them so he knows exactly what they want vs others are guessing. So you could end up randomly doing something the dragon really liked and that is how they end up lvling up vs MC who can now just easily cheat the system.