Yes, to "make a point of doing something", a person might write it down so they don't forget. Same as "I'll make a note to do that".
2. to wash one’s hands of = to decline responsibility, to rid oneself of the responsibility for…, refuse to accept responsibility for; abandon or renounce.
Yes, I think this derives from the Biblical passage where Pontius Pilate literally washes his hands of the blood of Jesus, and refuses to accept responsibility for what happened next. (If that wasn't the derivation, it certainly means the same thing).
3. a good sort (an easy-going sort) = a likeable, friendly person
An easy-going sort means what you say - someone who takes things casually and doesn't let things get to him (annoy him).
A "good sort" is an idiom for a desirable and sexy woman (or man). So don't call your friend a "good sort" if you mean "easy-going"!
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