Hmmm, I've never heard that protein is bad for breastmilk.
I can tell you that I'm still nursing my 2-year-old and I'm 5-1/2 weeks pregnant and I'm craving protein like crazy!
I don't love meat, but I am eating a good bit of chicken right now. Egg yolks, too...lots of egg yolks. For on-the-go protein, I like to eat hemp seeds or almonds by the hand-full. And I love black beans, garbanzo beans, and lentils. I also put 2 heaping tablespoons of pea protein on my cereal every morning and try to eat a cup of goat yogurt every day with my little boy (we don't do any cow's milk dairy).
I hope that helps you get some ideas for eating a bit more protein.
Also I didn't purposely try to keep my son from eating solids before age 1, but I'll tell ya...he LOVES the "nummies." He is still very much breastfed. Even our very breastfeeding friendly pediatrician can't believe how much he still nurses. But he's 30 pounds, 35 inches tall, has perfect iron and vitamin D levels, and has the most satin-flawless skin you've ever seen...he's a picture of health. So, while I would love for our nursing to back down a bit, I'm so glad he's still getting all the good nutrients from my breastmilk.
And if you want to stick to breastmilk alone till age 1, I don't think that's a problem at all. In those first few months, even first year, of trying solids, it's all experimenting anyway. They're not getting a ton of nutrients from the actual food. Just taste testing and beginning to build healthy habits of eating fresh fruits and veggies!
I hope that helps. Take care of yourself and sweet baby.