1. Provided you have the constraint in the missed approach procedure in the database, managed speed should stay at the maximum speed defined by constraint. Look up "6 Ps", could be important when operating to high elevation airfields with high terrain around.
2. If you're in IMC and by some coincidence you have 180 kts, just put flaps 2, select 160 and off you go. There is no restriction on extending the flaps again once you have started to retract them - and vice versa. If you're VMC, you can obviously judge whether you have sufficient terrain clearance.
3. All this debate about "no acceleration during the missed approach". All correct, but on a normal missed approach with 2 engines, the gradient will be much much above the minimum required, so you can easily level off (or reduce ROC) at one point, clean the aircraft and continue climb.
Of course keeping the speed restrictions is still nice thing to do, so you don't hit a mountain that was not taken into account during procedure design.