How much wrestling experience does he have? If it's a substantial amount, then personally I think it'd probably be a better gameplan to develop his ability to effectively close the distance (to gain either a clinch or takedown) than it would be to try to stay on the outside and out jab everyone.
Why not play to this strengths rather than trying to make him fight where he is least experienced? Sure, in the long run developing a solid striking skill set and evasiveness will be time well spent. But it's unlikely that you've got enough time to develop his striking to a high level (or at least not to the point his wrestling is at).
Even if he was mostly a counter wrestler he'll still probably find that he is a step (if not a few steps) above anyone other than maybe a better wrestler (or maybe very good judo player) at takedowns and top control/positioning once it hits the ground.
If the rules allow for strikes when on the ground, then he should be able to be pretty effective from the top (which is most likely where he'll wind up). Just drill the crap out of submission defense (and being aware of what he is open for and when) and work on GnP skills. It would also probably be a good idea to drill escapes should he find himself on his back (unlikely, but possible) and guard passing (which it looks like you're probably doing already).
I don't think it's best to limit yourself to an arbitrary number of strikes in a combo.
Sure, there is obviously a point when things become ridiculous (like 10 strikes without repositioning or not expecting your opponent to move, clinch, shoot a takedown, or strike back while this is happening), but if he gets overly used to only throwing 1-2 strike combos he will become predictable. Nothing wrong with doubling up the jab before you throw the right hand (overhand, straight, hook, whatever), or following the right hand with a left hook, or following a jab-straight right combination with a leg kick, etc...
The important thing isn't how many strikes are in each combination, but rather that he is picking his shots (not just wasting his strikes but throwing them with a specific purpose in mind), keeping in mind that at some point his opponent is likely going to counterstrike, or attempt to tie him up/take him down or "run" to gain distance and be ready for all three possibilities. Make sure that he keeps his other hand up in an effective guarding position when he throws any and all strikes.
Again, personally I would have him working on using his striking to close the distance to be able to use his strength (wrestling). That's where he's going to have the best chance of winning IMO. But, that's just my opinion.
Focus pads can be great, but their effectiveness is somewhat dependent on the person holding them. At first when someone is just learning how to actually throw the punches they can be good for developing accuracy or speed (tough to throw full power strikes on a focus mitt though). Later the holder can throw strikes back (forcing the fighter to evade or defend them) to give a more realistic feel.
Just make sure that (at least once he has the strikes down fairly well) you start to incorporate footwork with your focus mitt drills asap though. Ideally that means that he must close the gap effectively every time to land (at least) the first strike, involve some angular footwork into the combination somewhere (to open up targets, take away opponent's weapons, or facilitate takedowns), and always "close the door" on the way out (could be jabbing out, a leg kick, a fake, etc...) to make it harder for the opponent to follow him once the combination is over.
Honestly though, nothing beats actual live drilling (the level of intensity/resistance can obviously be adjusted to appropriate levels) of techniques though. Try some isolated sparring/drilling where one of you tries to land your jab and the other works on defending it. Gradually work in other punches (and kicks if you want) as his/your skill increases.
You always want to keep the level of resistance just high enough so that you both have to work hard and aren't always successful (because that's unrealistic), but also come away gaining something and feeling some level of success from the experience though. Like Iron Mike said in this seasons TUF "success breeds confidence, and confidence breeds success." Not only can the body only take so much of a pounding on a regular basis, but if say you are constantly dominating him and shutting him down, he may start to think self defeating thoughts, lose confidence in himself and possibly even lose motivation for training. If on the other hand he always comes away feeling like he improved/gained something from the training session, then his confidence will gradually improve and help him to succeed.