Questions if my menu calculations are correct

I agree there’s a large quantity of appetizers and main proteins.
However if it’s an hour or two of appetizers and drinks before dinner then i would keep the same generous quantity here.

You can reduce the salmon to closer to 16lbs and still have plenty.
I also agree to increase the amount of mac and cheese, it’s generally a crowd pleaser.
You could omit the cous cous all together and just have the mac and cheese and some bread or dinner rolls.
I do think you’re short on any veggies. For the salad i would have salad dressing on the side for people to add themselves, this will help prevent wilting before everyone is served.
As an addition roasted veggies are easy and could be made ahead the day before, just rewarm before serving. My favorite super easy trick for roasted veg is to toss the diced raw veggies in a basic vinegrette with generous salt and pepper **before** roasting, they come out of the oven ready to eat and perfectly seasoned

Agnes - have a look at this site or similar ones
https://www.chef-menus.com/food-quantity-chart.html
Compare what they recommend and modify based on what you know of your people (likes and dislikes, what kind of quantities they may have eaten in the past) and how much leftovers you want to cope with.
First reactions -
1) In general, there may be too much quantity in appetizers and mains (proteins) and not enough in sides (grains and vegetables).
2) If you're going to serve it at all, increase the mac & cheese amount. I've seen & heard of too many parties where the adults preferred the kids' food and raided it. Have enough so everyone can at least have a taste.
3) No dessert? Maybe include something tied to the occasion. Or something celebratory. Or a buffet - e.g. ice cream, pound cake, crepe or plain cookie as a base, with selection of toppings to customize for each guest. Depends on capacity of location to hold certain foods at hot or cold temps, and on number of servers.
Good luck, both with the planning and the event!

I forgot that I am also serving 60 pcs of empanadas as part of appetizer