Over the past few years I and my family have accumulated $35k worth of points for free. I have also redeemed them for travel worth around $15k. It is incredible to receive so much for free. I have some scruples now about doing this. Is this ethical?

I see it as the cost of doing business for large companies. Also in a way you are capitalizing off the stupidity of average Joe's. The average Joe signs up for the credit card and only accumulates debt. Thereby their loss is your gain.