Who told you to only learn one opening as black and one as white? You should know at least two.
The Alekhine is very tricky but objectively not so great, it's best used as a surprise weapon. I am sure you would have tremendous success with it if you wait for an opportune time to unleash it at club level. However learning the ins and outs of e5 would be a good idea.
In the old days a lot of even the world's best would only play d4 or e4, eg. Fischer. Nowadays it is quite rare. You are better off in playing different openings, you won't be so predictable then and I think it's psychologically better than just playing the same opening every time. THIS DOES NOT MEAN you play the Grunfeld one day and the Benko the next, then you give the Belgrade Gambit a try, it means you have two-three openings you have studied in depth you can use over many years. One idea that makes sense is having a solid opening (eg. queen's gambit declined) and an aggressive one (eg. dutch).
I am starting to take chess more seriously and just recently became a USCF member and will start playing OTB tournaments soon and join my local chess club. I'm obviously not a very strong player and was wondering at the 1500 - 1600 level is it necessary to have multiple responses to say e4? Right now online, I exclusively play Alekhine and would guess that in 70% plus of my games I have an edge by move 10. This is because I've really studied the opening hard and know it well. I've listened to the advice on here to not fall into the beginner's trap of learning so many openings and just learn one solid response to e4, one solid response to d4, and then as white know how to play e4 OR d4. Spend the rest of your study time on Middle game / End game stuff.
But live in tournaments and then in my local club I'm worried this approach may not work, as well because people will learn I play the Alekhine and prepare super well for it when they know they are going to play against me. Thoughts?
That also brings me to a second totally newbie question. Is there a way online to scout my openents who are USCF members to see their games (and by extension, for opponents to do the same for me once I have games under my belt)? I just joined a few days ago and I was trying to play around on the website to figure that out but couldn't seem to. I listen to Hanging Pawns (who plays in Europe) and he is always talking about how he scouts his opponents, and while I underestand how to do that for chess.com, I don't know how to do it for OTB games.