This is gonna be a quick one, I don’t have much to remark on this time
No corrections on this one, but one point of note: both 急 and 入っちゃってぇ express it’s something that came up suddenly.
This feels both a bit forced with the explicit mention of “in advance” and a bit strong with “thank god” - you’ve got the idea, but the “in advance” meaning of ～ておく doesn’t necessarily mean “in preparation for something” or whatever, just something you did beforehand. Considering the previous sentence and this being a surprise visit, something like “good thing I baked these” is enough.
なんか is something along the lines of “something like …” - so this is Tatsu suggesting playing the game (and being open to other suggestions), not so much him asking what kind of game to play (which would be strange anyway considering what follows).
Yes - in addition to the lawsuit-happy nature of Nintendo as mentioned by @MrGeneric, it’s just common practice to slightly change popular brand names, so you’ll get things like WcDonald’s, Bepsi and Burger Queen.
Japan doesn’t have fair use laws around copyright, so making use of a company name legal in any way, shape or form requires written approval from said company. Most publishers and authors opt to change the name in favour of going through the hassle.
ケツモチ refers to something like the Yakuza cleanup crew (referring to disposing of evidence and such), so I’d say this is more like “leave it to the cleaners” - but it’s not wrong per se, since he does mean himself
どう is how rather than if, so this is “how you make things right” rather than “whether you can fix them or not”
I gotta say, you’re making noticeable progress It’s mostly some nuances and minor things here and there but no outright mistakes (as far as I can tell anyway), and your only point of (mild) confusion was the use of Morio instead of Mario. Do you notice reading this manga is getting easier for you by this point?