'Turn over a new leaf' = start something new = 'opened a new chapter'.

'In the teeth of' = in direct opposition to / despite.

'In cold blood' = deliberately and without emotion = calculated.

'Beggars description' = too extreme to be described in words.

'Verbose' = using more words than needed.

Milton's stated purpose: 'justify the ways of God to men'.

'A round dozen' = exactly twelve = a full dozen.

'Soft soap' = use flattery to get what you want.

'Complacent' = smugly uncritical and unaware of danger.

'Officious' = annoyingly eager to help; meddlesome.

'Supercilious' = arrogant. Opposite: 'Affable' = friendly and approachable.

Present perfect needs past participle. 'Lay (eggs)' past participle = 'laid'.

'Paint something + color' — no preposition needed.

Embedded question uses statement word order: Subject + Verb.

O. Henry was the pen name of William Sydney Porter.

'By' = means or agent. Villages lit 'by means of' electricity.

'Come off' = to take place as planned.

'Dog days' = the hottest most sultry period of summer.