If I play Divine Judgment, I'd rather recycle my remaining runes over 2 (other than the ones used to pay for Divine Judgment itself) for power rather than no effect. Can I wait to see if my opponent responds to Divine Judgment with something like Abandon before doing so? What if they recycle their own runes for power?

No — you can't wait and see. When your Divine Judgment finalizes, you're the first player to receive priority (you control the chain's only item, Rule 337.4). If you pass to wait for your opponent and they simply pass, all players have passed in sequence and Divine Judgment resolves immediately (Rule 339.1) — your spare runes get recycled by its effect for nothing, and you never get another window to activate your own runes' "Recycle this: [Reaction] — Add [C]" ability (Rule 164.2.b).

Your only guaranteed window to recycle your own runes for power is right after playing Divine Judgment, before you pass priority. If you want the power without the gamble, recycle your spare runes (keep your best 2) before playing Divine Judgment in your Main Phase — the power floats until end of turn (Rule 167). The only downside is if Divine Judgment gets countered, you've spent runes for power you may not need.

If your opponent does respond — with Abandon or by recycling their own runes — the chain reopens and you get priority again before Divine Judgment resolves (Rule 340.4), so you can recycle your runes then. If they recycle their own runes for power, yes, that gives you a window: their rune-recycle is an Add ability that finalizes and resolves immediately (Rule 429.2), and when they pass you get priority. They're doing the same math you are — their spare runes were getting recycled either way — and their recycled runes leave the board, so they'll have fewer left to protect when Divine Judgment resolves.