No about 30% at least.. I was considering operational range of the battery on a trip of about 90%-20% (70%), lose 10% for highway speeds, 30% for cold, 5% degradation. So range between charges on a trip is (100-30-10-5) *70% = ~38.5% of the battery or ~120 miles. Forget about towing.
Needing to replace the battery in 7-8 years would be terrible longevity. No way it should need replacing already, the warranty is 8 years and it should last longer than that.
Don't believe 300+ is real though. Normally you will be only using the 80-20% portion of the pack between charges, add in cold, highway speeds, and degradation, your actual range will only be about 40% of that so more like 120+.