I have a 3 year old and 23 month old and a new one due in may. I exclusively nursed them until 6 months and then we started with the cereal and fruits/veggies gradually. The main difference between stages 1 & 2 are that you get a bit more variety and they begin combining flavors. Because of this, you just want to be sure he's tried each individual ingredient before giving a combination to isolate allergies. Otherwise, you really don't need to worry too much.
I made basically all of my kids' babyfoods. It was just easier for me. So, I just started with single veggies and fruits and tried them for about 3 days to watch for reactions. If nothing happened, we moved on to new things. We avoided citrus and strawberries as they are supposed to be harsh for their little systems and possible allergens. I'd make a bit more than my husband and I would eat and let it cook a few minutes longer to get extra soft, toss it in the food processor and then scoop into ice cube trays and freeze. Once froze, you pop them out and toss in a labeled baggie and then pull out and warm up for meals...perfect portions. As I noticed my little ones wanting more food, I'll pull out a double portion or started mixing 2 different items to make it a bit more interesting - so basically making my own stage 2 foods.
You should just be able to follow your son's lead on quantity. If he seems hungry still, go ahead and offer him another couple bites. By 8 months, he will probably not drink quite as much milk as he did before 6, but formula/breastmilk are still really their primary source of nutrients until age 1 so don't cut it back too much. I always started offering a sippy with water at all meals when we introduced foods. You could also put formula in a sippy during meals by now to start getting him interested in that. My little ones got teeth early so we were also started on finger foods before 8 months. Gerber "puffs" are great as an early one - they basically melt in their mouths so it's pretty hard for them to choke and they like them. It's a great activity to keep them busy while you're eating too. It's a lot of work to pick them up and get them into their mouths! Mine liked the biter biscuits too for teething, but they do break off in pretty big pieces as they soften from the little one chewing/sucking on them. So you do have to watch carefully. You can also try frozen bagels and cheerios. Cheerios are good once they learn how to deal with the puffs in their mouths since they don't completely disolve - they do have to munch a bit for them to go down properly.
Try not to get too hung up on the details - introduce foods individually and watch for allergies and otherwise, go with your instinct and enjoy this new adventure. It's really not so important if your little one eats new foods in a particular order or quantity. What works for each is different. If something doesn't seem right, check with the ped.