Welcome. I'm not sure what a pressure barrel is, but the hand pump is a problem. Unless you brew in batches that you can drink relatively quickly, it's not a good idea to introduce oxygen to the beer. They don't like each other. Most of us use CO2 or a combination of CO2 and Nitrogen to push the beer.
For your second question. Aging beer is a good idea. Aging it cold is even better. I find that when I put my kegs in the fridge (usually takes a month or two to finish off a keg) the first pint is pretty good. The second to last pint is award worthy - the last pint is very disappointing, I think I'm drawing another great pint, then "phbtbtbtbt!" and half a glass of sediment!
Adding cane sugar to raise the alcohol content will work, but will cause a cidery flavor. It's best just to add more malt extract. Honey is popular also, but doesn't ferment very well. If you use a lot of honey, it's probably also a good idea to add yeast nutrient. Good luck!
The way to tell your alcohol content is to measure your wort's specific gravity prior to fermenting, then after fermenting. You use a hydrometer for this. Then there are several places on the web you can look to get the ABV based on these two numbers.