Having gotten married within the last couple of years (at age 24), both of our parents contributed. We did not pay for much. However, that is usually one of the first things to figure out- how much can parents contribute or better yet, how much are they willing to? You are NOT obligated to pay for anything (except as was stated, it is TRADITION to do a groom's dinner). ANyways, as I was saying, once everyone (including the bride and groom) know what is "on the table", THEN they can plan around that budget. They can't just say, "Hey, I want a dream wedding with 300 guests". You plan a wedding around what you have to work with, same with much of life. And that will be a lesson to them- you want a dream wedding, figure out a way to put more on the table yourselves. You want a better car, house, etc, same sort of deal. You can't rely on your parents after 18 to fulfill your dreams so to speak.

Anyways, you obviously are caring and feel pressured already since you are posting it. I would honestly just put it out there- "I wish I could do more, but X is the max I can contribute" and if he doesn't understand with your financial situation and all you've already done for him, then maybe this is a good lesson for him because he should NOT feel entitled to your help anymore.

Also, if you can't contribute much financially, see if there are other ways you can help- decorating, organizing, planning, etc. Some of that is priceless, although sometimes brides feel the less the mother-in-law helps with those sorts of things, the better! Sometimes they want your help financially but do not want your help or input...

Stay strong and good luck!