Welcome to the Forums!
We're glad you are here!! Cute pig, he looks almost exactly like one of my boars, except without a crown.
Do you use corncob bedding? It isn't recommended, maybe you could get Aspen, or Carefresh? Kiln Dried pine is also cool. No ceder or regular pine, because they cause URI. Also, what size cage are you making? What you have now is probably the Extra Large cage, it's the largest that I got at my feed store, when I wasn't enlightened by the wonders of the c&c cage... wow, that sounded so dorky! Haha. You are OK right now with the cage size, because it is equivalent to a 1x3, the size of a 2x2, which some say is big enough for one pig granted floor time. I would recommend a 2x4 and up, only because I, myself, think a 2x3 is too small, but many people claim it's huge! I guess it's because I started out with a 3x3 and made my way up to a 4x6, and a 2x6.
The little seed mixture treat type thing is crap, it's not good at all. The seeds can cause choking and sometimes death. Seeds, coloring, nuts are not good for guinea pigs at all, have no nutritional value and most store bought pellets have deadly ingredients in them.
www.oxbowhay.com has the best pellets, really, they are practically the only good pellets. Don't use mineral wheels, or salt, ect. Kaytee hay is sometimes really bad, but I've heard that's the only hay some pigs will eat. Maybe you should try all different types of hay to see which one your pig loves the most.
How many times do you have to clean that cage? I had one and literally had to clean it every 2-3 days, but I had more guinea pigs in there than you have(Again, I didn't not know the whole space issue) but all got floor time. Does he get floor time? He looks so cute and so healthy, I'm sure you are a great mum/dad(Sorry, don't know.... lol).
Do you know what veggies and fruits to feed? If not, I'm sure all of us here can help you figure that out. Good luck with your piggy!