At what point does someone count as disabled? How difficult does something need to be, or how painful or distressing does something need to be, before it counts as a disability? Does a given action need to be 100% physically impossible 100% of the time, and if not then that person is just lazy and deserves to be expected to power through it? (I am the person who is frequently being expected to power through things, which is why I'm asking.)
In addition, there are things like, say, lifting extremely heavy weights, that almost nobody on the planet can do. What proportion of the population needs to be capable of doing something before not being capable of doing it counts as a disability?
Bottom line is I'm struggling a lot and I have frequently been on the verge of suicide at the prospect of doing several different things, a few of which I have actually succeeded in doing at the expense of extreme physical pain and/or mental distress, and I don't know if I have the right to consider myself disabled or not.
generally the best advice to give people is to give them the tools to evaluate disability enough to be secure in the fact that they are disabled, not disabled but have a health condition, or just not disabled at all. but I'm gonna be honest, causing significant and long-term distress is a qualifier of disability. i don't know the actual limits of what you can or cannot do, but you have to admit that most abled people don't want to die instead of doing tasks. you can call yourself disabled. you are unable to do certain (basic? essential? necessary?) tasks that would support you to live independently. also wrt to your question about how "unable" does someone have to be at a task for it to count, consider the metric that you should be able to do it:
safely (i.e. not at risk to yourself or others. are you always hurting yourself trying to do this task?)
unaided (e.g. without specific medical tools, someone else with you, someone prompting you to do it, etc )
regularly (!!! you have to be able to do it more than once at a reasonable timescale. for example if you can eat without supervision once a week but 6 days a week you need supervision then that's not regular enough)
also to be frank, whether or not you feel comfortable calling yourself disabled has no impact on the fact that you are struggling. i wish being disabled was an acceptable reason for other people to acknowledge your difficulties, but often it isn't. the mindset you have encountered about "powering through" is classic societal ableism and they will tell this to anyone, no matter how impaired. i still think it's meaningful to realise that you are indeed disabled when you are, but you don't have to be disabled to struggle. and you don't have to have to meet a threshold of suffering or distress to be worthy or deserving of help. whatever you can do to make your life more bearable to live, i suggest you go for it.