Don't give up! You've been working so hard at this. And you are not forcing something horrible on him. Giving him substandard nutrition for the rest of his infancy is far worse than letting him struggle at the breast for a few weeks or a month. I know it's hard feeling like your older child is neglected.... but really, a few weeks is not going to make a difference. My 6-year- old and my 3-year-old LOVE when I tell them stories. How about spending some of your pumping time telling stories to your older child, or some similar activity that does not require physical activity on your part?
There will be no need for a guilt trip because you are NOT going to fail. Just get that out of your mind. YOU WILL GET THERE. You have plenty of persistence, you just need a little patience!