A coupleof questions:
1. How do I deal with the FG Little Mac's. I've assumed the role of counterpuncher and am having more success, but its still very difficult. What moves are easier to bait and punish?
2. Regarding the double jab > smash. I am using the twice button press method for the jabs, then flicking c-stick. Though sometimes when pressing the button twice the kicks come. Am I pressing the buttons or flicking c-stick too fast?
1) Just camp out in the corner of the stage and force their apporach with your blaster. Just don't shoot too much because Little Mac can easily punish you with his dash attack. Just poke him once with one laser here or there to send the message that if they (Little Mac players) want to win, they must meet you at the ledge.
Next, grabbing out of shield is your best friend here, since his dash attack is easily punishable by combos (namely Grab out of shield ---> Dthrow ---> Fair) If he dash grabs you, so be it. He can't follow-up any of his grabs and he can't contest you off-stage. Also, your Up-tilt strings can be countered or DI'd out of, so you need to see his response to your combos and adjust accordingly. For example, if he's countering your 3rd Up-tilt, then wait after your second one and charge a Smash.
Your Fair/Nair and especially your RAR Bair (if you can pull it off) are good enough to gimp Little Mac. Just pay attention to what he does when recovering. Does he counter? Does he air dodge? Does he recover high? Does he fast fall into Up B right under the ledge? If you can read his recovery patterns then you can get an easy two-stock on him.
However, you need to wary of him breaking your shield, Little Mac's smashes put a good dent into your shield, and if your shield is low enough, a well-timed Fsmash from him will ruin your day.
If he's using a lot of smashes, I recommend rolling away or jumping away and reposition. His Down smash will catch anyone rolling around him so you need to be careful about rolling behind him if he's using his D smash. If he's mainly using tilts and jabs, your shield is a safe option. If you're uncomfortable with Mac being in your space, your Fox Illusion (Side B) can come in handy here.
Lastly, your D-smash is very strong against Little Mac because of the low trajectory of the attack. Heck, even your F-throw at the ledge can be enough to finish him.
2)
Fox's Double Jab Combo (YouTube link)
You're tapping A too fast. An alternative to pressing A twice is pressing and holding A until Fox throws out his two jabs, then releasing A. Rinse and repeat.