Learn Farsi: من از اینکه خزه شاداب است و نمی‌پوسد شگفت‌زده هستم. - I am surprised that the moss is fresh and does not rot.

In Farsi, the adjective shegeft-zade requires the preposition az (meaning surprised by or from). When a prepositional verb or adjective is followed by a full clause rather than a simple noun, we must insert inke (this that) to act as a bridge. So, az inke literally means "from this that."

The sentence starts with man (I) but ends with shegeft-zade hastam (am surprised). Is it normal to put the whole "that" clause in the middle?

Yes! Farsi strongly prefers keeping the main verb phrase at the very end of the sentence. The main frame of the sentence is man ... shegeft-zade hastam (I ... am surprised). The entire explanation clause starting with az inke is simply tucked into the middle, right before the main verb.

Why are the verbs in the "that" clause (ast, nemi-pusad) in the present indicative tense instead of the subjunctive?

We use the normal indicative tense here because the clause states an objective, existing fact: the moss is fresh and does not rot. If the clause expressed a hope, doubt, or a hypothetical situation, you would use the subjunctive mood instead.

How does the word shegeft-zade (surprised) break down?

It is a compound made of shegeft (wonder or surprise) and the suffix -zade (struck). Literally, it means "wonder-struck." You will see this suffix on other words to mean being overcome or hit by something, such as (frozen, literally "ice-struck").