4 is equivalent to: "...how loved you are in my heart, and how loved you are in my mind". This is likely your intended meaning.
3, however, uses "lovable" which means "deserving of love". Difference: "you are loved (by me)" = I love you. "you are lovable" = you are endearing to people. This does not use an object phrase such as "by me". It is a trait.
"how I am delighted" vs. "how delighted I am"
4 is equivalent to: "...how loved you are in my heart, and how loved you are in my mind". This is likely your intended meaning.
3, however, uses "lovable" which means "deserving of love". Difference:
"you are loved (by me)" = I love you.
"you are lovable" = you are endearing to people. This does not use an object phrase such as "by me". It is a trait.