JFly - I have a BLW baby who is a gannet one day and a waif the next, and as you may remember his weight gain has always been abysmal so I do stress about it... It can be incredibly tedious when he's on a disinterested day so you have my sympathies. I've found sitting with him very attentively makes a huge difference, as does making a big song and dance about me tasting it and looking ecstatic and saying yum very loudly. Effusive praise for every morsel (tedious in extremis when he eats a whole grated carrot piece by tiny piece as he did on Wednesday...) and a firm no for throwing or messing. It also really helps if I eat the same as him and show him that it is the same.
On food, bread is a huge favourite, so I try to do things that involve breadcrumbs (basically make whatever you have into a patty, dip in flour, then egg, then breadcrumbs, and fry or bake). Pancakes are great for protein, carbs and fat and can be stuffed savoury (e.g. cheese sauce with spinach and brocc, or ratatouille with cheddar) or sweet (banana or apple and cinnamon). Egg rolls are a similarly good protein idea - make very thin omelette then spread with cream cheese, layer with veggies then roll up.
I try not to worry about too much bread - it is a good carb after all - and just try to get more creative with filling. Philly or hummus with whatever veg you like grated into it is fab, so you can ring the changes with the veg while DS thinks he is getting the same favourite. Leftover risotto was wolfed down the other day, so I'm planning to try every version under the sun of that.
MB is right - AK's chicken and apple things are fab. Also if you don't have it, I like Finger Foods by Jennie Maizels and I've got most of my ideas from that, including a very healthy but surprisingly yummy sandwich filling - cream cheese, lentils and spinach.
Finally, my top tip is to take DS out for lunch once a week. I really noticed on holiday that DS loved the razzamatazz of watching waiters and other diners. He liked watching the food come to the table and trying new things, and I get to experience a change of scene. Plus I get ideas for cooking for him - planning to make Thai sweetcorn fritters this weekend after they were a hit, and did egg fried rice today after successful Chinese meal.