Mephistopheles has three bits of Latin:
Solámen míseris sócios habuísse dolóris.
Solamen is ‘consolation’ – relative, not interrogative – miseris is ‘to/for the wretched/miserable’, socios (related to ‘social, society, associate’) is ‘companions, associates, allies’ (plural direct object), habuisse is a perfect infinitive ‘to have had’, and doloris is ‘of pain, sorrow, trouble’. Put together, it means ‘(it is) a consolation to the [plural] wretched to have had companions of [=in] sorrow’, pretty much ‘misery loves company’ but more concrete (‘miserable/wretched people’ for ‘misery’) and with a past tense added.
The line is a complete Latin dactylic hexameter, which mixes spondees with the dactyls in the first five feet, and ends with a spondee: in this case we have one spondee, then four dactyls, then a spondee to end the line. It looks like a quotation, but if so the author is unknown: perhaps Marlowe composed it himself. As with Wagner’s Qui mihi discipulus, we can read it according to the Latin rules, like this, or we can give the words their proper prose accents, like this. The second half sounds pretty much the same either way.
Per inaequálem mótum respéctu tótius.
This is a tedious bit of scholastic Latin prose, pseudoscientific jargon that doesn’t really answer Faustus’ question. Why do different planets pass each other in their courses around the sun, or even sometimes appear to back up (‘retrograde motion’ as in the All’s Well joke)? ‘Through [= because of] the unequal motion in respect of the whole’. Mephistopheles doesn’t know enough, or care enough, to give a more precise scientific answer. It should sound something like this.
SUH-muhm BO-nuhm. This is two trochees, and the Us all sound like the U in English ‘put’ or ‘push’. Summum is ‘highest’ (as in ‘summit’ and ‘sum’ and ‘summary’), and bonum is ‘good’ (= ‘good thing’ – neuter adjective used as a noun, as in English). It’s philosophical Latin: the ‘highest good’ is whatever is most important in life – pleasure for Epicureans, duty for Stoics, God’s will (I think) for Christians, and so on. It should sound something like this.