I think while ideally you don't want him to cut back on the milk to take solids, I think sometimes you do have to cut it a bit to give them an appetite for food.
I had to with my ds - he is now formula fed as I am back at work (why do I feel I always have to justify that...... ) but prior to weaning he was on 40 oz a day - a LOT!!!! Now I give him half his milk feed, then about 20 mins later offer solids, followed by a top up of milk again afterwards if he wants it.
This has stopped him cutting back on his milk too much - he still has more than the recommended 20 oz a day - but has given him an appetite for solids. I know you're breast feeding but could you try something similar?? One boob before solids and the other after?
Also, it took him a while to figure out that eating solids stopped him feeling hungry, IYSWIM. If he was properly hungry he was only interested in the bottle, and would yell if I offered solids at that point ( he doesn't any more as he's worked it out and happily yells for his solids now......!!)
I would also try more finger food as some hate being fed from a spoon. My ds loves sucking on segments of orange, and happily eats mango, cucumber, banana etc. It didn't happen immediately, but keep offering it to him, helping him to pick bits up if they are very slippery, and I'm sure he'll get the hang of it.
HTH