My babe is also 8 months, and not really eating much at all in the way of solid foods. She loves to gnaw on an apple slice, have bits of sweet potato (I usually cube and roast them with butter/CO oil and seasonings), minuscule bits of tender meats, tiny pieces of banana, drops of my smoothie, etc. I haven't forced the issue, because I do think they eat when they are ready (barring any medical/sensory issues).
Focus on nutrient-dense foods from your plate. If he isn't ready for finger foods, just mash it up a bit and feed it from a spoon. I think you're right, that anything before a year or so is really more for the experience of food than for the nutrition for most babies. I don't have a problem with letting my baby have fruit, mostly because of this reason; my babies have all been nursing pretty heavily at this point, so what little fruit they get at 8 months is just tastes.
As they gradually eat more solids, I try to make sure that there is plenty of fat in the diet: butter on veggies, whole milk kefir in the smoothie, egg yolk, etc. I also limit grains for a very long time; this babe hasn't had any yet (well, I think she found a random cheerio on the floor the other day, but otherwise...), and I'm not in a hurry to introduce them. Even after a year, I'll still be slow to give them to her.
It sounds to me like you are on the right track. As far as how much and how often, if I don't have something readily available, she doesn't get anything at that meal. She might get something once or twice a day, or not at all. Every day is different. Your baby may want more food, and that's ok. I do try to make sure that she is still nursing frequently (I aim for at least 6 times per day, ymmv), and she nurses several times in the night. If I felt like solid food was overtaking nursing, I would definitely cut back on it, and offer to nurse more often.