First of all, I agree with the poster who said they don't like it when people attribute differences like this to male female. While there are significant differences in the way girls and boys develop, there is no difference in activity level that is attributed to gender. My daughter, for example, completely fits the description you gave for your son. Some babies are calm, some are active. The difference is that society (and many parents and relatives) rewards active boys and tells girl they need to be calm and loving and play with babies... I could go on because the whole system makes me mad, but that is not the point.
However, the same poster said that at 8 months they can "manipulate" and that you have to "nip it in the bud." While I know what she is saying, that is a really negative and defeatist way to look at it. However, the post immediately preceeding me was a lot more on the spot- kids this age are starting to be a lot more aware, but they can't express their needs and desires so it makes them frustrated. To encourage more independant play, set him up to succeed (like the other poster said), look around your environment for anything he can interact with (kitchens are a great source, pots and pans, bowls, containers with lids, large utinsils, anything not sharp or breakable). Give him the chance to explore these things while you are otherwise occupied (nearby, but try not to watch intently because they know when we're watching). I always had problems getting Izzy to play independantly, but from birth I put her down often and wouldn't pick her up/play with her right when she started to fuss, I let her fuss a little, and now I tell her "I can't hold you, I'm busy." And she has gotten better. Try reading "Your Child At Play" for the ages 0-1, and 1-2- they will give you a lot of great ideas to get him stimulated. And use lots of words to help him develop his vocabulary- he probably won't start to talk for a few months, but talking to him will help him learn fast and help him feel less frustrated because you know how he is feeling. The signing idea was great, too- this is actually the perfect age to start it because some kids will pick it up right away (but don't be discouraged if he doesn't- my daughter didn't pick up more than 2 signs, and she now has an AMAZING vocabulary). The best way to begin signing is to buy the little board books (the ones by Dr. Acredolo and Dr. Goodwyn, particularly the ones with photos of babies instead of cartoons) and read them to him, and show him the signs yourself. The videos are okay- I like "Baby Signing Times" better than "Baby Signs" but my preference is irrelivant since they didn't work for us! It really helps if they just learn "more" "all done" "drink" and "eat" because those cover the basic needs. Anyhow, just learning a few signs will help him to communicate with you, which will reduce frustration. That said, now is the time to lay the groundwork, so to speak, for discipline. Obviously he can't use words vs. whining yet, but the minute he learns a word require him to use it when he wants that thing- don't listen to whining. I taught my daugther to say "please" so that even if she didn't know the word she could point and use a word instead of whining. And if you say no, don't back down! If you say "no" to something and he cries tell him "I know you're mad I said no, but ___(reason you said no stated as simply as possible)___ Now is also a good time to establish a routine if you haven't already. It is so much more important for toddlers not just because it helps make sure their needs are met (well rested and fed so they don't have those added frustrations), but also because it gives toddlers a sense of control over their environment if they know what is going to happen and when.
I know how you feel- having a child like this is hard work, but I don't think I would change it because she is so sharp and entertaining! But I'm not going to lie, I do hope this next baby is a little more relaxed.