I don't even know where to begin. My older son has severe peanut (possibly all nuts as we haven't re-tested yet) and sesame allergies.
First, get all that peanut butter that you all love so much and anything with nuts out of the house ASAP. His first reaction was very severe and they can only get worse from there, not better. If we eat out without our son and it has something with nuts or sesame, we wash up real well and brush our teeth.
Second, get several Epipen Jr's. Keep in your purse, diaper bag, car, day-care, preschool if he goes to one, in the house. Also do the same with Benadryl. They have the Children's perfect measure spoons which are convenient because you can keep them with the Epis everywhere (check with the allergist for the dose for your son's age and weight).
Sesame and peanuts allergies go hand in hand many times so I would keep him away from the hummus for a while until you get him tested for sesame as well. Hummus is made with tahini which is made from sesame paste.
I wouldn't worry too much about peanut and sesame oils as the oils don't have proteins in them. My son has the highest level of peanut and sesame allergies yet can do fine when I cook with those oils or buy something with those oils.
Start shopping at places like Wholefoods because they have a lot of products that are made in nut free facilities. Also, many products today are made in facilities that process nuts but use good manfucatoring processes to prevent cross contamination and I do buy those products and he does fine on them.
It takes a while to do grocery shopping ever since we found out (when he was about your son's age; also with an ER trip). I also have a baby with multiple food allergies (none life threatening so far thank G-d).
The Food and Allergy Network is a good source. There are also support groups. I am still looking for good resources myself. When you go out to eat, always clean the table and other surfaces your son will touch with a baby wipe first (my son actually had a reaction to touching a table that wasn't properly cleaned). Always ask the waiter to ask the chef what the ingredients are and say you are asking because of an allergy. Many restaurants now have allergy alerts when they put in your order so the chef knows to be extra careful.
Plan play dates only with parents that are willing to take the extra precautions of washing their child's hands and mouth. Preferably have play dates only at your house.
When you go to the park watch other kids carefuly.
It's not an easy life. It's easy to get deperssed about all the parties your kid will be missing out on and stuff like that. But it is what it is and you just have to learn to live with it.
When our kids are older, they can start understanding and start watching out for themselves as well
When you put him in preschool, look for a school that is either nut free (like we have) or is very supportive.
Good luck and let me know if you have any more questions