I know this is a fairly old thread, but I noticed this wasn't responded to. Not that I'm particularly well-versed in Latin, much less with M Aurelius, though I feel like this deserves some answers.
Regarding nam si delirare ... visis impelli
, I'd say that literally visis impelli
could be translated as "to be driven [pres. pass. inf] by visions [n.: abl. pl. nt. of 'visus']", which would then make sense.
As to your second question, it's only a personal attempt, but it seems to me that most of it consists of indirect discourse, triggered by 'hoc' and 'illud', hence 'obscurum esse' being an infinitive. To translate it literally:
Not only should this be considered [hoc being the subject accusative of oportet], that
life is being diminished each day and that a small part of one is being left behind, but even 'that' [illud] must be considered, that
even if anyone [si/nisi/ne/num + quis/etc. = someone, anyone] were to be alive [note that it could be either from vinco or vivo, but the latter really just makes more sense here; see Perseus
] for a longer time, it would be nonetheless unclear, whether ... etc.
As for the mood : a concessive clause introduced by etiamsi
can take the indicative or subjunctive, as per normal conditional clauses (i.e. based on its factual nature), so in this case I'd say the subjunctive is there for that reason. However, the verb in that clause would have had to been subjunctive in either case, since it's a subordinate clause within an indirect statement, and all verbs in those require the subjunctive.
That seems to make sense for me, but perhaps I've missed something. In any case, if you haven't received any other sources by now, hopefully that helps to some extent.