• saṁśrāntau — exhausted
  Dual past participle of sam-√śram. Apparent exhaustion is part of manuṣya-ceṣṭā; Sūta's verb is grammatically dual to emphasize that even Balarāma joins the performance — the līlā is two-handed.
• pravarṣaṇa-ākhyam — known as Pravarṣaṇa
  Compound: pra-√vṛṣ (to rain heavily) + ākhya (named). The mountain's name literally means 'much-raining.' That Kṛṣṇa picks this peak for the upcoming fire-leap pastime sets up Indra's element (rain) against Jarāsandha's element (fire) as a quiet doctrinal counterpoint.
• varṣati — he rains
  Third-person present of √vṛṣ (to rain) — the very verb that names the mountain Pravarṣaṇa. Indra, called bhagavān as a courtesy of office, makes the rain fall here ceaselessly. Gauḍīyas read such usage in the Bhāgavatam as preserving the hierarchy: even devatās are 'lords' within their domain, but Kṛṣṇa is Bhagavān without qualification.

• Where could 'apparent exhaustion' on high ground be the right strategic positioning?
• What 'incessant rain' might cover your real plan?

Pravarṣaṇa is Indra's rain-fountain mountain — the very peak where heaven's water never stops falling — and on top of it the two Lords pretend to be tired. The mountain that drinks Indra's clouds becomes a footstool for the One whom Indra worships; the apparent exhaustion is the comedy that conceals the ownership.