You cvould be wrinting about my son until very recently. He is 3.9, and from Christmas 2005 to Christmas 2006, He was almost exactly as you hsve described yours. In this time, I had, pretty much, a nervous breaakdown while pregnant, had a baby, nearly split up with dp, had £50 of make up destroyed, all my earings poked down the plu hole, a newly decorated lounge redecorated in wax cray lipstick and nail varnish, I have had to pu bolts on my bedroom, the kitchen and the bathroom door.. the list goes on.
he was late to speak, he still pooed his pants regulrly until 3.5, and yet 4 months later, he really is a different child.
the key with him was exercise and very very clear rules with not too much explaining. Once we had sorted that (and it was bloody hard work) the destructiveness slowed
Also, nd p[lease don't think I am getting at you here because I'm not, but once my mental health improved, ds1s behavior improved dramatically.
Ds1 needs vast amounts of exercise to stisfy him. I take him to an enclosed area and park myself by the gate so he can't get out. Then i stand and challange him to run here there everywhere, faster fastwer fster, almost like throwing a ball for a dog
And although he doesn't run away now, at your son's age he did, and that meant wherever he was somewhere he could escape from, he wore reins, end of. But every day we leave the house, rain or shine. And i still heap mondo amounts of praise on his head for coming back.
the very clear rules, basically I would almost do it by rote.
"Ds1." Repeat name until response.
"Please do X/ stop doing X."
(he would usually ignore me)
(me) "If you don't do blahblah I will count to 3 and when I get to three you are going to your room and I will shut the door. One, two, three" then do it. I didn't look at him or talk to him, but I would carry him upstairs, into bedroom, and hold the door shut until he stopped raging and waws calm. Then go in and be nice, as he had just been taught a lesson.
I'm not boasting, I haver been lucky, and he isn't a very defiant child anyway, but he mostly does it by the time I gat to two now.
But it has taken a few months, and I do feel a lot of the change is simply tht he has grown up a but. he is 50 times more mature than he was 6 months ago, at the age your ds is now.