Just reiterating some points with a bit more context, cause yeah
30+ is not old for grad students. On average, the youngest one can be when finishing their phd is 27 (assuming you didn't skip any grades in school or got your masters thesis upgraded to phd). Its very common for people to only finish their phds in their mid 30s, and you're still considered a young researcher even after phd untill you're like 40.
I cannot stress enough how poor everyone in gradschool is, like, unless you have some sort of generational wealth, you are wearing clothes you've patched by hand, likely the same jeans you've had since highschool, and still eating instant noodles pretty much every day.
On the subject of food, grad students will take every opportunity for free food. This means that if theres snacks at an event, the gradstudent is likely eating half the platter and trying to take the leftovers home, cause this may be the only variety theyve had in their diet for months.
On the subject of being poor, no one in these fics is complaining about ridiculous university fees, like parking and admin fees, nearly enough
On the subject of admin, no one is complaining about that nearly enough either. Your gradstudent character should go on at least one rant per chapter about how ridiculous it is that the school/research foundation/lab/whatever wants yet another progress report, or how godawful the registration process is, or how their funding is getting held up again cause the uni has once again misplaced some of their documents, and how this is keeping them from doing their research
Grad students have virtually no free time. When you're not working on your thesis (which takes up about 10-12 hours a day, including weekends), you're TAing an undergrad class or working in the lab, and pretty much any moment you're not doing either of those, you're likely doing your mandatory volunteer work. TA'ing and working for the lab is only paid work sometimes tho, and usually it doesn't pay much anyway.
Going to a confrence is often one of the most exciting parts of being a grad student. You are contractually obligated to go to at least one confrence a year, but these are nice, it often means an opportunity for international travel, and a break from at least the TA work and volunteering, where for at least a week your accommodation, travel, and food costs are completely covered. This is basically heaven.
Also on academia being unhinged, yeah, it just is, and the above examples are great, but academia is also much more casually unhinged, like, I was retelling a story about how some theologian flipped a table over a disagreement, and my phd supervisor, an established researcher, just went "I wanna flip a table." Due to the stress of everyday life in academia, we are all always one minor inconvenience away from flipping a table, some are just more open to admitting it than others