Nobody with anxiety should be drinking alcohol if they can't cope with the symptoms. Why? Well, drinking alcohol temporarily raises serotonin levels in a burst, then lowers them. Trying to counter the sedative affects of alcohol, while you think you're relaxing, the nervous system actually puts the body into a state of hyperactivity. Along with a drop in blood sugar and dehydration (alcohol acts as a diuretic), this can cause palpitations, dizziness, confusion, nervousness, muscle weakness, shaking and sleep deprivation. Alcohol circulates in your system for around 12 hours... yeah, been through that experience a few too many times myself. Not fun.
Good news that your heart is normal from the recent ECGs. Actually, anxiety releases chemicals in your body during palpitations to protect your heart.. no damage happening. I had the same symptoms as you at 23, and 7 years later, even after literally days of non-stop palpitations, I'm still here and OK :D
If you want to look after your heart better, eat Omega-3 in the form of fish oils. You're doing Paleo, so that should be helping, right?