Brewed my first one gallon "experimental" batch tonight

It's not that you shouldn't put more than a gallon into a one gallon jug... Point is you need to put a lot less than a gallon into a one gallon jug. At this point, I'd rig a blow-off tube/receptacle and accept that fact that I'm losing some wort/beer. What's left at the end will still be beer.

 

Pretty much this. In the future if you have a gallon jug do a 3/4 of a gallon batch or look for a 2 gallon jug and do 1.5 gallon batches and so on.

 

I make only 1 gallon batches, and use the entire pack of yeast (rehydrated of course) in each 1 gallon batch. There is no harm in over pitching the yeast.

 

add base malts and do a partial mash. you won't regret it

 

http://www.howtobrew.com/section3/chapter18-3.html

Partial Mash

 

One gallon batches are easily mashed brew in a bag-style on the stovetop. Most pot and pan kitchen sets come with a 1.5 gallon stockpot you can use as a mashtun. Your boil kettle functions as a sparge vessel. You just need to buy a grain bag sold at most homebrew shops.

I had a problem with that technique on the one gallon batches because you don't have enough thermal mass in the mash to maintain consistent mash temperatures so I upgraded to a two gallon water cooler. Works very well.

 

There's really not that much difference in the process. Mashing is steeping the grains at a specific temperature for a specific amount of time. Then you sparge (rinse) the grains. The difference when you steep you are just letting the specialty grain character seep out of the grain into the water but you don't get fermentable sugars. When you mash you are using the enzymes in the grain to convert grain starches into fermentable sugars. When you mash specialty malts you are effectively steeping them along with the base malts. You could steep your specialty malts while mashing your base grain (and some authors do suggest it).