This is called a nominativus cum infinitivo, which is possible with intellegitur because the finite verb is passive. Debeo normally has a mere infinitive with it, so there is no indirect statement there either. There is no indirect speech, no accusativus cum infinitivo.
An a.c.i. cuts through the sentence, separating main clause from indirect statement, such ...
Yes, your supposition is correct about the two singular nominatives agreeing with a plural verb:
317. Two or more singular subjects take a verb in the plural.
Pater et avus mortuī sunt. His father and grandfather are dead.
(Allen and Greenough, Latin Grammar)
However, the sense of pareo is to submit to:
Fame and glory submit to riches.
To answer your ...