I am answering this question to the best of my ability, but I am not a doctor. So keep that in mind.
I have had a blood clot(DVT); your brothers symptoms that you have described, some of them sound similar to the symptoms I had when I had my blood clot. I had serious complications from waiting too long to seek help My blood clot broke free and traveled to my lung -which is called a Pulmonary Embolism- and felt like someone had sucked punched me in the chest and caved my lung in. I was in the hospital for 24 days while they dissolved that with Heparin. Then, due to a condition I did not even know I had(Factor 5), when I went home on Coumadin(a blood thinner) I had a triple brain bleed and catastrophic stroke. I had to be life flighted to a med center for traumatic brain injuries and was there for another 51 days. When I was finally released -to a long term care and rehabilitation center- it took 19 months there, and another 3 years to get back to about 80% of where I was. And I was lucky.
What I am saying is take, make, beg your brother to go to the ER NOW, while it is still just a blood clot. As far as the meth use, no, they cannot arrest him for having used meth. That's not to say that he will not face disdain and judgement and straight discrimination(a lot of medical personnel are of the school of thought that if a person is a drug user[and that is what he will be labeled as, even if he used it only one time] they are somehow less deserving of medical care. Don't let that stop you from going) but I would still say he should tell the doctor the truth. A doctor can help you only as far as you inform him; if you leave that out, it could be an important detail and could be something that would then cause an undesirable result(you know, like death) directly because of the doctor not knowing. Since it has been over 3 days and your brother is only a very casual user, it most probably will not show up on a drug test. I hope that helps. I must stress though that just because it will not be found on the drug panel does not mean your brother should not disclose he used it with the doctor.