I have a Cremina 83 and I too was having problem getting good result from the 4 holes. I've tried fitting the 2011 steam wand, Espro 12 oz pitcher, Motta 8.5oz picther, gallons of water with dish soap. No help there. At least not true silky microfoam.

1) I am using one hole now. THe result is very encouraging,no visible bubbles and definitely latte art worthy. But then recently I had Crossland CC1 and the microfoam actually feels like liquid, not cream. Maybe that's the silky drink you're looking for. It's a wake up call for me to notch up my microfoam on Cremina.
2) Block all the holes except one. Using as high pressure as you could without burning the coffee.
3) THe expansion doesn't matter that much I think. The recommended expansion is about 33-50% if I remember correctly, but I've managed to expand near 100%(almost double) and actually get creamy microfoam with 1 hole(no visible bubbles). Still it's not as liquidy as the one I got from CC1.
4) I hope they're talking about silky drink. Even 'microfoam' from 4 holes with visible bubbles could pour a decent art, so latte art isn't the best measurement for microfoam

Depends on the pressurestat setting - at a about 1 bar with my PonteVecchio, at least, a four-hole (or maybe 3-hole?) tip will bring a cappuccino or two's milk up to "Dutch Boy" latex consistency in less than 30 secs.

In fact, I usually inch up the pstat until it just gets to the pressure where it will do a good job steaming, but not too much so the boiler does not run too hot.

PC