Rubor in cute interdum manet, etiam cum dolor iam minor est.

Because rubor is the subject of manet. The sentence is saying that the redness remains, so rubor is the thing doing the action of the verb.

• rubor = redness
• manet = remains

So rubor must be nominative singular.

Because in can take either the ablative or the accusative, depending on meaning.

• in + ablative = in / on a place, with the idea of location
• in + accusative = into / onto a place, with the idea of motion toward

Here the meaning is location: the redness remains in the skin. So Latin uses the ablative:

• cute = ablative singular of cutis

If the sentence were about movement into the skin, then in cutem would make sense instead.

Cute is the ablative singular of cutis, cutis, a feminine third-declension noun meaning skin.

Its basic forms are:

• nominative singular: cutis
• genitive singular: cutis
• ablative singular: cute

So in cute literally means in the skin or on the skin, depending on context.

Interdum is an adverb meaning sometimes, at times, or occasionally.

It modifies the verb manet, so the idea is:

• rubor ... interdum manet = the redness sometimes remains

It tells you how often the redness remains.

Manet is present tense, third person singular, from maneo, manere.

• manet = he/she/it remains

Latin often uses the present for general statements or typical situations, just as English does. The sentence is describing a general medical-type observation, so the present is natural.

No. Here cum is a conjunction, not the preposition meaning with.

There are two common words cum in Latin:

• cum
  • ablative = with
• cum as a conjunction = when, since, although, or similar, depending on context

In this sentence, cum dolor iam minor est means something like when the pain is already less. With etiam, the phrase becomes even when.

Etiam means even, also, or still, depending on context. Here it strengthens cum:

• cum = when
• etiam cum = even when

So the sentence means that the redness sometimes remains even when the pain has already become less.

Because dolor is the subject of est in the clause cum dolor iam minor est.

That clause literally means:

• dolor = the pain
• minor = less / smaller / milder
• est = is

So dolor is the thing being described as minor, and it therefore stands in the nominative.

Minor is the comparative form of an adjective meaning smaller, less, or milder.

Here it agrees with dolor:

• dolor = masculine nominative singular
• minor = masculine/feminine nominative singular comparative

So dolor iam minor est means the pain is now less or the pain is already milder.

Because in Latin a comparative adjective can stand by itself when the meaning is obvious from context.

So:

• dolor minor est = literally the pain is less

English often also does this: The pain is less. We do not need to repeat a noun like severity. Latin works the same way here.

Iam means now or already. In this sentence, already is probably the best sense.

• dolor iam minor est = the pain is already less

This suggests a contrast: the pain has begun to improve, but the redness may still remain.

Not really. Latin word order is more flexible than English word order, because the grammatical endings show each word’s role.

The sentence is arranged in a natural Latin way:

• Rubor — topic/subject first
• in cute — where it is
• interdum manet — the main statement
• etiam cum dolor iam minor est — added circumstance

A very literal rearrangement into a more English-like order would be:

• Rubor interdum manet in cute, etiam cum dolor iam minor est.

But the original Latin sounds perfectly normal.

Yes. Rubor can mean redness, blushing, or a red color, depending on context. In a medical sentence like this one, it clearly means redness as a symptom.

So here it is not emotional blushing, but physical redness of the skin.

Both can be possible depending on context, but in English on the skin may sound more natural for visible redness. Latin in with the ablative can cover location in a broader way than English sometimes does.

So grammatically:

• in cute = in the skin

But idiomatic English might prefer:

• on the skin
• in the skin

depending on how the larger text is phrased. The Latin itself is fine.