I do this quite often. You use more CO2 than you would with smaller kegs but like you I find 5 gal cheaper to acquire. Also, I like the option to brew more if I wanted and use the same kegs.
I haven't run into any issues with oxidation as long as purge as cjhammel stated above.
If purged...
I brewed a couple of the recipes out of that book a couple of years back and found that almost every one was way over carbed. None as bad as you experienced but all much higher than I expected. Almost all the recipes call for similar amounts of syrup, honey or some other household sugar.
It is...
Check out http://www.tampabay.com/topics/specials/craft-beer.page. The main page has a map with local breweries. CCB is probably the best overall but try to hit as many as can they all are pretty good.
Also, fyi, CCB just started serving food in the tap room, http://t.co/cIA5DlJnur
That is not true, in fact the exact opposite happens. Water expands once it is frozen. It will contract as it melts to room temperature.
Of note though, you will want to check your volume measurements.
Try to fill as much remaining space in the freezer with liquid, so add some water bottles, extra carboy filled with water, etc.
A freezer or any closed refrigeration unit will keep temperatures more constant the fuller they are. Air is not a good insulator so if you only have 5 gallons or so of...