Maybe this one?
English Made Easy Volume One: A New ESL Approach: Learning English Through Pictures (Free Online Audio) https://www.amazon.com/dp/0804845247/ref=cm_sw_r_cp_api_glt_fabc_76WKMQRHCJDXBC2P71W4
YouTube has some great sites. This one has been highly recommended to me by my Farsi-English friends.
Lots of listening. Can you set him up with a buddy who might like to have some conversation? Having a partner who is willing to speak slowly and answer many questions can be very useful.
These books just use pictures and context and are great for teaching students English when there may not be access to their original language. I used them when tutoring ESL and then now I use them in reverse to learn Farsi, though it's definitely easier to use in English because you can study and review the words after discussing them 1:1.
For you, Teaching English Grammar by Jim Scrivener can be very useful because it teaches you how to present grammar topics to students whose first language is not English and some of the problems they may have in learning that topic. I always consult it when teaching a new grammar topic to someone whose first language is not English.
Hope that helps!
Oh, PS Mango Languages has Farsi. I don't know if you have access to that or not.