Thanks for the chapter!
MC definitely an antihero at best. Granted he's been kidnapped to help out in their war but they haven't said there's no way to send him back and are treating him courteously. Also, what can they pay him as the local currency probably isn't worth much back home and there's probably a limit on how much they can send with him assuming they can send him back. Agree the other heroes are emotional, muscle brained morons. Rather than have him explain what they don't understand they assume he's a 2nd rate magician. Also, in a war logistics is very important. Unless weapons and armor have a self-repair function or can never be damaged it's going to wear out eventually, especially if used for OP attacks or defense even if just fighting weak small fry over and over. That's one of the reasons why those collecting monster parts use a special knife rather than their weapons. Also, unlike games there aren't going to be few if any inns or shops where the entire party can rest or purchase food without worry near the front line much less inside enemy territory. Hence camping gear, water, tent, sleeping bag, extra clothes, toiletries, tools and food have to be carried. So unless the kingdom can teach the item box skill or have bags of holding which can slow/stop time inside while carrying a lot the hero party are either going to need a secure supply line with fast response, carry it themselves, or if nothing else carry it themselves. While games usually have almost infinite inventory and can carry everything without issue it's a major hassle in the real world.
As for the maid and her former boss it's unfortunate that there are many in high positions who feel entitled to more and feel it's either a worthwhile or insignificant sacrifice to sell out their king, country, and innocent bystanders for money, power and influence. Although considering what horrible characters they are why do they always have so many fanatically loyal subordinates willing to do anything including die for them?