AJ against mini 3 bet from donkey

Fold.

You are in the seat after the donkey and will have plenty of chances to play IP postflop vs him, and that way take his money without much lotto.

Hero, 338 hands is about normal sample to check f23b stat, but it is not enough to check f24b. Your sample is quite small to use this stat (just look 7(7)). To me it an easy fold preflop most of the time without good enough sample, but sometime with good enough sample and FE I would 4B. In this case you probably need to fold. Just let take a look at 2 things
1) Your are out of position on the flop
2) let's suppose AXX bord comes in. What kind of hands would call your 4b IP? QQ(6), AK(12),AQs(4). So, you, probably, will exploit your self on the post flop with overplaying your A. If you know how will you win - ok - let's 4b. But most of players will easily give up for small pots and will give you a repulse for big pots.

I would fold. I don't usually cold 4bet as a bluff. Especially out of position.

Agree with the fold.