First of all---there is a LOT of variation in what is normal, so don't worry. I don't think his intake is unusual. Pretty soon he'll be starting to eat more and more table food and the number of ounces he'll eat at a sitting will be almost impossible to tabulate--and that's ok! I have NO IDEA how much solid food DD eats (11 months). She eats until she's done. If she fusses and her tray is empty, we offer more. If she still fusses (or if she fusses while there's food on her tray), we put her down. She eats (pretty much) what we eat. Bottom line, she's growing fine, so we don't worry about it. Don't worry about your DS eating too much--it is really pretty unusual for babies to overeat. Just trust his cues, and let him tell you when he's had enough, and offer healthy food, just like you are doing anyway.
As you wean your breast milk, your DS will probably start taking more solids on his own. Try to offer him plenty of finger foods so he can control how much he eats, though if he likes purees too it's fine to offer those as well. Around 1 year you can introduce whole cow's milk as a substitute for the breast milk. If you really cut back on the nursing before 12 months then you may want to offer some formula. By 1 year of age most babies are taking 12-24 oz of milk per day (again that's an average... but if you go much higher than 24 oz/day you can run into issues with iron deficiency anemia and constipation once you switch to whole milk)
Another thought--since you are pregnant--I wonder if he is eating solids so well because he is not getting as much at the breast as you think (due to decreased supply)?? This is not to make you feel bad or think you should supplement--if he is growing fine I wouldn't worry--but that may be why he is eating more solids than some other kids his age. Kudos to you for offering it to him!
Finally, between 12-28 months, the growth rate starts to slow down so kids all eat a bit less than they used to. This is quite alarming to many families but it may be a welcome change for you guys, LOL!
Hope that's helpful!
My sweet boy 8/06
My beautiful girl 10/09