Fun game! This has a lot of potential to improve.
The shooter section is pretty decent, but could use more bullet
patterns/enemies. It's very simple at the moment, and Stage 2 feels like purely a test of how much HP you got before you arrived.
A few new enemies could help alleviate this. If you're feeling lazy, find some patterns from one of those danmaku games (e.g. Touhou) and put them in. They'd work fine.
Oh, and the difficulty's just fine too.
The stuffing content is alright, but having to watch the same progression over and over while doing the repetitive task of eating is tedious. It's good content, but accessing it isn't fun.
I really like the mechanic of controlling Yuri's arm and being able to throw items. I think this should be expanded upon.
When the mouse cursor is over the Back button, Yuri looks like she's stretching. It's pretty cute. Some kind of face change when the player hovers over the Back button to properly show that she's stretching would be a nice addition.
Leaning far forward at high fullness levels leads to Yuri's stomach appearing to phase through the chair below her. I think a neat (and appreciated) touch would be to have it squash against the chair, making it so she can't lean over as far. It would add to the physicality of the belly.
I know this is a stuffing game, but some weight gain seems appropriate. One doesn't eat constantly every day and spend most of their time in a cockpit and not gain a few pounds. A way to lose pounds and still stuff to high capacities could be a best-of-both-worlds situation, although that would mean creating a lot more art assets.
Really, what I think this game needs is more. More mechanics for shooting, more mechanics for eating, more options than just "pick who to feed" with your crewmates. I hope you revisit this game and add more to it someday.