"Maybe the Sun was much closer to the Earth"

Yes, I should have been more precise. I should have said the earth would have to have been much deeper in the sun's gravity well. Either way, if the distance between earth and sun had been substantially less a billion years ago than it is today, we wouldn't be here to have this conversation.

The comment about "losing so much mass" relates, I assume, to the matter the sun has lost through conversion to energy. In its 5+ billion years of life, the sun has lost less than 10% of its original mass through fusion. This wouldn't come close to explaining how it could have ever produced tides on earth comparable to lunar tides.