Watch him now: he hastily straightened his tiger-skin kilt, came out at the gate, and said to the Great Immortal, "Set your mind at rest, sir — I go, and I return.

你看他, watch him now, is the storyteller talking over the action to his listeners -- a reminder that this novel began life as something performed aloud. 虎皮裙 is the tiger-skin kilt Wukong has worn since his mountain days. 就去就來 is I'll go and be straight back.

But you must serve my master well — three teas and six meals a day, every day, with nothing wanting; and if the least bit is short, old Monkey will settle accounts with you when he returns, and stave in the bottom of your cauldron first of all.

好生伏侍 is to wait on somebody properly. 三茶六飯, three teas and six meals, is a set phrase for hospitality laid on without stint -- full board with extras. 算帳, settle the account, is still exactly what a Chinese speaker says when threatening to get even. Wukong uses it in mock menace and then ruins the effect by adding a threat about the cooking pot.

When his clothes are soiled, starch and wash them for him.

禳 (ráng) normally belongs to exorcism, but here it is doing colloquial duty for grimy or soiled, standing in for 穰. 漿洗 is to starch and wash; doubling it conveys doing the job thoroughly.

Let his face grow the least bit sallow, and I'll not have it; let him lose the least bit of flesh, and you shall not stir from your gate."

The line is built out of 些兒 (xiē er), the least little bit, repeated until the fussing itself becomes the joke -- not an ounce off him, not a shade of colour. 不出門, you shall not leave the house, is Wukong sentencing an immortal patriarch to be grounded. The 兒 is the toneless er.

The Great Immortal said, "Go, go — I will surely not let him go hungry."

定不教他忍餓, I certainly will not let him go hungry. 教 is jiào here, the reading that means to let or make someone do a thing. Zhenyuan is humouring him, in the tone of a host who has worked out that the shortest road to peace is agreement.