Do my watts look normal?

Looks fine to me. wattage drops seems to follow cadence which makes sense.

Looks like your PM is working.  The spikes are normal as well.  

Now go read the book.  

the book is a great tool. read up. study. get really fast.

In general, 260-280 watts to go 19 mph and 300-330 watts to go 22 mph is pretty high considering the flat profile.  But impossible to pinpoint unless we know your frontal profile, wind conditions, road surface, and even choice of tires.  

You should get used to doing the manual zero offset as well as the auto zero by pedaling backwards.

I don't see anything to get excited about. Go get at least a few decent rides in before you start thinking about changing things.

the 910 automatically uses 1s recording. do not change this.  there is a display field that allows you to view the 3s average power, which is what most people use.  

"smoothing" the data is done after the data is uploaded and just gets rid of any spikes to make the profile easier to read and see trends.  not sure if garmin connect does this, but there is other software out there that will.  i'd recommend getting golden cheetah and learning how to use it with your power data.

for now though don't worry about any of the data. get a solid month of data before trying to base your training off of it.

Yours makes more sense to me. I'd expect a little more speed for that power for me as we're similar height, but I'm noticeably lighter and even riding upright (as you were) I'm still fairly far over. Is your friend really short or drafting a lot somehow? That seems really low for the speed.

its kind of high, but still doesn't seem like something is wrong to me. i group ride with a guy that weighs 20-30 more pounds that me and will put out 30-50 more watts... and he never pulls. 

are you calibrating(zero'ing) your power meter before you start riding?

About the average cadence thing...

I found my garmin just averages it over the entire ride so when you freewheel, it will lower your average.  I found "average" cadence to be worthless unless doing a TT or something.  Cadence is only helpful on it's own as a real time number. 

You can use analytic cycling to play around with some numbers.

http://www.analyticcycling.com/ForcesSpeed_Page.html

Of course this assumes that you are riding constant, without any stop signs, turns, or anything to slow down for.

If I make some rough estimates for you.

0.75 frontal area (you're a big guy and were riding up on the horns)
0.5 drag coefficient (don't touch this)
1.226 air density (looks like your ride is at sea level)
105 kg
0.005 crr (assuming good but not perfect roads)
0.00 slope
240 watts

You get 9.41 m/s (multiply by 2.23694 to convert) or 21 mph.  But take into consideration all the braking you had to do for the turns, and you're in the ball park.  Maybe the watts are a little low.

Now take your friend's data

0.5 frontal area (he's still a big guy but probably riding his aero bars)
0.5 drag
1.226 air density
102 kg
0.005 crr
0.00 slope
144 watts

You get 8.69 m/s or 19.4 mph.

As running2far mentioned, it's impossible to know who's power number is right.  Maybe they are both right...or both wrong and need servicing.  But just thought that I'd throw the calculator out there so you can play around with it yourself.  Power is fun. 

Edit: this calculator doesn't factor in wind or possible drafting opportunities that may or may not have existed in either ride...adding to the complication...but the calculator is still fun to play with and gives you an idea of how crr, frontal area, and power make a difference...and some make more differences than others...especially when comparing flat to uphill efforts.