God, I hate my boss. You know what? I'm gonna turn him into a woman and marry him and live with him and fuck him and have a child with him. Wait a minute.
I have a possible explanation for the first issue. Both 田 and 井 are common surname endings and look rather similar. So the scene may be used to illustrate that Tsunoda is so forgettable and unimportant that even his colleagues don't care to properly remember his name, and he's used to this to the point that he doesn't even bother to correct people anymore.
Ah, I mixed up the characters, sorry. However, this still may be the indicator of the director being sloppy with names, as he's the only one who refers to Tsunoda as Tsunoi both times on pages 4 and 29 (where you mistakenly put Marui). Sort of a running gag, perhaps. Also, on page 14 when Marui speaks about the surname, he likely meant that Ryoko's surname is now Marui too as their marriage had been registered.
@IIoydo-kun For the sentence on page 16, if you break it down like this: *熱いの* で お腹の中満たされちゃう then it can be translated to: My belly is completly filled by *the hot stuff* and that will probably make more sense.