Good for you for working so hard to give your baby the best of everything!
The logic behind nursing first and the offering solids is to reduce frustration if baby is reluctant to try something new, and also because solid food at this age is merely an introduction, an opportunity to sample textures and experiment with eating. Ideally, your milk is his primary source of nutrition for the entire first year. Think of solids more as amusement than hearty nutrition--especially since most of baby's first foods are relatively low in fat, and your milk is wonderfully creamy and full of things to help him grow.
Still, if he will put up with it, no harm done by offering him lunch foods before a lunch nursing so you can get home to him and reduce your headaches and the mental gymnastics of timing pumpings and nursings.
To reduce pumping sessions, you could consider "stretching" your stored milk by mixing your milk with single-grain cereal so he could have some of your milk with a sample of solid foods.
You might appreciate the books "Working Mother, Nursing Mother," "Hirkani's Daughters," and "Whole Foods for the Whole Family," and "Whole Foods for Babies and Toddlers." They are all published by La Leche League and contain information that is hard to find elsewhere. The first two, in particular, are gems. The legend of Hirkani is about a woman from an ancient village in India who climbed an enormous gate and scaled down a cliff so she could return to her home and nurse her baby. The king honored her bravery in mothering and there's a village named for her today. The book is a collection of essays from moms in all sorts of employment,from factory workers to brain surgeons, who combine working and breastfeeding. It's very cool and uplifting. You could find any of those books pretty cheap online from Amazon, buy them directly from LLL (www.llli.org) or borrow them for free from your local LLL group.
The fact that you only work part-time means you can often be available to nurse your son on other days, which is great for your milk supply.
I agree actually feeding a baby is a big pain compared to nursing. . . I'm a big fan of anything I can do laying down or with my eyes closed and without dirtying a dish I'll have to wash later! I have introduced solid food very slowly to my three boys and it's nice to keep it simple and slow so they can eventually have bits and pieces from my plate and not need too many spcially-prepared foods.
Best wishes!