While i do agree that it is extremely important to be cautious in situations like the one you were in, i do have to commend you for offering to work in his store for free. It's a shame to hear that he passed away and i'm sorry for your loss.
Personally, I have learned so much by working in a LFS (i'm 18 and i started working at your age), especially in regards to customer service and how retail environments work. So even if you aren't working for an actual paycheck, i'm sure you gained a lot. Hopefully you will be able to find a new store to work at in the event that Something Fishy closes its doors.
This looks like a cool project, and i wish you the best of luck!
Thanks, It was very sad news for our club and he will be dearly missed.