i read the light novel and it seems that there is a Person who actually brought him into another world and helps him with these two cheat like abilities.so there is no Company behind this :) the plot is really good.
also considering that he killed every single Dragon there and even the Dragon god/deity gives him alot of exp. I think the only one capable of killing a Dragon was ONE hero long ago and of course the demons/demon lords.
I agree, also if the enemy is @ a higher level and is killed doesn't the exp multiply depending on the level difference.
he was level 1 and they were minimum level 50, but not all games have that. I am glad he can hide his level.
As a gamer, that experience he gained at that one instance is freaking impossible. You can't just jump that many levels with monsters at that level. At best his level should be a third of what it is... Either he has a cheat account/the company is really generous with their levels or bug. probably a bug.