Flatten under 1/2 underlay?

[Mark Brown]

LOL

I won't bother getting started then, but lets just say I feel your pain. Laminate has hit the pinnacle of its existence... just in time for people to turn their back on it

 

[highup]

If you have access to a hardwood floor edging sander at a rental place, see if you can get some 16 grit paper for it. For flattening high spots, comparing a belt sander to an edger sander is like comparing the hamster to a honey badger.
You will be emptying the bag very often. I hook mine up to my 16 gallon shop vac instead of using a bag.