Yes. Your understanding is good.
Let me point to specific places in the sutta, so that others can follow it:
1. The verse you quoted first “Sukhavinicchayaṁ jaññā; sukhavinicchayaṁ ñatvā ajjhattaṁ sukhamanuyuñjeyya” is the beginning of a new section here (labeled 9.1):
“Araṇavibhaṅga Sutta”
– There, the Buddha first describes sukha vedana experienced by anariyas (average humans) who attach to kama guna and indulge in sensual pleasures:
“9.1‘Sukhavinicchayaṁ jaññā; 9.2sukhavinicchayaṁ ñatvā ajjhattaṁ sukhamanuyuñjeyyā’ti—9.3iti kho panetaṁ vuttaṁ. Kiñcetaṁ paṭicca vuttaṁ? 9.4Pañcime, bhikkhave, kāmaguṇā. 9.5Katame pañca? 9.6Cakkhuviññeyyā rūpā iṭṭhā kantā manāpā piyarūpā kāmūpasaṁhitā rajanīyā, 9.7sotaviññeyyā saddā … 9.8ghānaviññeyyā gandhā … 9.9jivhāviññeyyā rasā … 9.10kāyaviññeyyā phoṭṭhabbā iṭṭhā kantā manāpā piyarūpā kāmūpasaṁhitā rajanīyā—9.11ime kho, bhikkhave, pañca kāmaguṇā. 9.12Yaṁ kho, bhikkhave, ime pañca kāmaguṇe paṭicca uppajjati sukhaṁ somanassaṁ idaṁ vuccati kāmasukhaṁ mīḷhasukhaṁ puthujjanasukhaṁ anariyasukhaṁ.
2. Then, (as you mentioned) the Buddha describes the (Ariya) jhanic sukha experienced by those who attain Ariya jhana via the removal of kama raga anusaya. That starts at 9.13 in the above link:
“9.13‘Na āsevitabbaṁ, na bhāvetabbaṁ, na bahulīkātabbaṁ, bhāyitabbaṁ etassa sukhassā’ti—vadāmi. 9.14Idha, bhikkhave, bhikkhu vivicceva kāmehi vivicca akusalehi dhammehi savitakkaṁ savicāraṁ vivekajaṁ pītisukhaṁ paṭhamaṁ jhānaṁ upasampajja viharati. 9.15Vitakkavicārānaṁ vūpasamā ajjhattaṁ sampasādanaṁ cetaso ekodibhāvaṁ avitakkaṁ avicāraṁ samādhijaṁ pītisukhaṁ dutiyaṁ jhānaṁ upasampajja viharati. 9.16Pītiyā ca virāgā upekkhako ca viharati …pe… tatiyaṁ jhānaṁ …pe… 9.17catutthaṁ jhānaṁ upasampajja viharati. 9.18Idaṁ vuccati nekkhammasukhaṁ pavivekasukhaṁ upasamasukhaṁ sambodhisukhaṁ. 9.19‘Āsevitabbaṁ, bhāvetabbaṁ, bahulīkātabbaṁ, na bhāyitabbaṁ etassa sukhassā’ti—vadāmi. 9.20‘Sukhavinicchayaṁ jaññā; 9.21sukhavinicchayaṁ ñatvā ajjhattaṁ sukhamanuyuñjeyyā’ti—9.22iti yaṁ taṁ vuttaṁ idametaṁ paṭicca vuttaṁ.”
– The verse at 9.18: “Idaṁ vuccati nekkhammasukhaṁ pavivekasukhaṁ upasamasukhaṁ sambodhisukhaṁ.” is translated correctly as: “This is called the pleasure of renunciation, the pleasure of seclusion, the pleasure of peace, the pleasure of awakening.”
That could be stated a little better as: “This is called the pleasure of renunciation of sensual pleasures, the pleasure of release from mental agitation (viveka), the pleasure of getting samma samadhi (away from kāmasukha and attakilamathānuyoga,) the pleasure of awakening.”
3. The verse, “Rahovādaṁ na bhāseyya, sammukhā na khīṇaṁ bhaṇe’ti” related to your question comes at 10.1.
-Yes. The English translation there is good. If you read the rest of it, it will become clearer.
– The point is the following: When one comprehends the anicca, dukkha, and anatta nature of this world, it will be easier to engage in such behavior. One just needs to be mindful.
4. Your comment about the Buddha advising bhikkhus to cultivate jhana is valid.
– “Idha, bhikkhave, bhikkhu vivicceva kāmehi vivicca akusalehi dhammehi savitakkaṁ savicāraṁ vivekajaṁ pītisukhaṁ paṭhamaṁ jhānaṁ upasampajja viharati.”
– It is impossible for “householders” to truly abstain from sensual pleasures and eliminate kama raga anusaya. They can get to anariya jhana (that holds only during this life; some lose the ability to get into jhana even before this life ends, as happened to Devadatta) but not Ariya jhana.
– P.S. If a Sotapanna attains an anariya jhana, it is unlikely they will lose it before dying. Thus, they will be born in a Brahma realm (not a suddhavasa Brahma realm) and attain Arahanthood from there. Thus Sotapannas with anariya jhana are also Angamis, in the sense that they will not return to kama loka.