Those e-bike rides with average HR in the low 100s shouldn't be viewed at exercise at all. Your diet should be prepared as if the bike rides don't exist, because it cardiovascular terms, they don't. A typical person of average health will have a similar energy output while walking at a normal pace.
An intake of 2200-2400kcal/day is high for someone weighing 186lbs unless they are particularly active. Absolutely discard Garmin's calorie numbers, even if they're coming from the e-bike's PM. The Garmin thinks you're doing all the work. The above-mentioned 45 mile ride would be in the 1200-1300kcal area without assist, if it were done at ~17mph. To reach 1500 would require it to be really steep, or ridden really quickly.
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