Upon repeated viewings.... (spoilers)

1. I see what you’re saying, the Nostromo was undoubtedly large but it was still just a towing vessel, picture a tug boat in comparison to the size of the ships they maneuver, they’re relatively large, sure, but tiny in comparison to their counterparts. I think a 7 person crew for a towing vessel is fair. And yes, the company was most certainly conducting business on the cheap.
I mean Dallas has to pay for that final meal out of his own pocket, “I’m buying,” I didn’t take that as Dallas being cute or figurative, I interpreted it as the crew is allowed X amount of meals per day and anything outside of that comes out of their pockets.

2. Not sure, maybe a means of clearing the lines?

3. I think it was meant to be, the company (especially this company, given what we know about them) would make it so to protect their ship, cargo, investment, also as a way to account for human, dumbshit error. Lots of stupid people out there doing all kinds of idiotic things.

4. Not sure, maybe someone else can chime in?

2. To look cool. The same as spinner cars in Blade Runner. Made no sense in technical sense, but looked cool.

3. It was, on purpose. So that nobody would accidentally turn it on.

1. We need to clarify what the Nostromo is. The Nostromo is this part of the structure / unit that we see at the very beginning of the movie:

https://www.belloflostsouls.net/wp-content/uploads/2021/09/Nostromo-project-moc-lego-alien.jpg

The other part is the refinery part of the unit:

https://static.wikia.nocookie.net/avp/images/6/6c/Tesotek_2100-B_refinery.png/revision/latest?cb=20230315001009

So the Nostromo itself is like the tractor part of a semi truck, something like this:

https://m.media-amazon.com/images/I/71npkRBfj+L._AC_SX679_.jpg

... and that is hauling the refinery.

With all that: that's still a very big ship, and of course the refinery part might need repairs as well, but I think the Company's rationale makes sense in the context of the film: having a 2 man repair crew is the bare minimum that they can get away with, so any life threatening situations can be handled by at least 1 of the crew (if the other is sick, incapacitated, etc.), and everything else can be finished in however many hours 2 people need to work on.

Also, my assumption is that the refinery itself must be much more robust than the ship, so it very rarely needs on the fly repairs, all the malfunctions or failures that present themselves can be treated on Earth or on any of the planets that has a repair dock.

2. I think those options for ventilating various gases are for the maintenance crew.

A real life example would be the crash of Helios Airways Flight 522 - where the cabin and cockpit pressurization switch was set to "manual" after the maintenance crew forgot to switch it back to "automatic". That switch is something that you would never use during normal operation of the plane, you never want to purposefully depressurize the plane... but it's there if you know where to look. Venting potentially harmful gases inside the passenger area of a spaceship is not a good idea - but for maintenance purposes, it might make sense - as does the pressurization switch on a plane. And Ripley, knowing her way around the pod, thinking on her feet remembered this option from her training, so it shows her as someone who is resourceful and is able to find a solution under pressure (no pun intended).

Details of the plane crash can be found here:

https://en.wikipedia.org/wiki/Helios_Airways_Flight_522

3. Yes, and there are two reasons for this. First, from a filmmaking point of view, the movie needed to show how determined Ripley was to initiate the SD. Jumping through that many hoops indicates she is fed up with the situation and means business. And later, when all this needs to be done in reverse - the movie shows how desperate she is to be on time... and she is not. So she finds herself in a calamity again and needs to escape to the pod. So characterization and building suspense.

But it makes sense in universe as well. If you want to blow up a ship that is really-really expensive (42 million dollars - adjusted!), you damn well be sure of the reason why. So it is kind of an approval process - if you do all this, you really mean it, so off you go.

4. The filmmakers modeled the scenario after the Titanic, which had an insufficient number of lifeboats. It also plays into the hubris and corporate greed idea. However - there is still a great deal of confusion surrounding this among the fanbase (and in the Nostromo model builders subculture!). This question was not properly explored in the film - see the main article and the comments here:

http://alienexplorations.blogspot.com/1979/10/confusion-about-number-of-nostromos.html

Even the URL is confusing :-) The number of "Nostromos" is not in question (there is only 1 Nostromo in the film, as discussed in my reply to your very first question in this thread), but the number of "Narcissuses" - is I think what the URL should have been. But well... confusion.

The simple solution for this would have been to have the crew shortly discuss that there are 2 escape shuttles, but the other one is out of commission for some reason, and repairing it is not possible until they reach a repair dock somewhere. That would have addressed this once and for all. The way it is presented in the movie is nonsensical, as Ripley refers to "the" shuttle, which implies there are no other means of escape, should a self destruct be initiated... Which is not corporate greed, it's a case of blatant disregard for really basic safety requirements - but then again - Titanic... It is not completely out of the realm of possibilities for W-Y to be that scummy, but it's hard to stomach the crew going along with it. So mentioning a second, inoperable shuttle would have clarified this question.

Alas, we never got word of a second shuttle. If there was a second shuttle, the crew would have abandoned ship immediately after the death of Dallas, so from plot perspective they needed to create a situation where they are not able to leave the ship, unless there are only three left. Understandable, but handled a bit sloppily, I'll give you that.