As per the calculations from the Karvonen Heart Rate. Your maximum H.R. should be 152.
Maintaining your heart rate between 50 percent and 80 percent of its maximum is enough to provide cardio benefits.
At 178 you're doing anaerobic not aerobic exercise.
Your resting h.r. of 76 is that taken before getting out of bed in the morning? That's how it should be done!
I suggest seeing your doctor first.