To understand the difference between Love and Kindness you have to appreciate the idea of Sacrifice . Kindness is often a response to compassion and therefore can be given with little or no sacrifice on the part of the giver. When a billionaire donates one hundred thousand pounds rot a good cause or charity this would definitely rate as an act of Kindness but not one of love.
On the other hand Love is an act of empathy that the giver has had to walk in the shoes of the recipient by denying themselves something that relates to the suffering of the for said recipient . A struggling employee might have trouble work several hours to find the money to hand over to the needy.
It is vitally important that compassion and empathy are not confused. Giving of our time can both be a reflection of Love and Kindness as a kind act includes a sacrifice of our most precious resource time. It is also stimulated by compassion to take some action to help the other.
The other might not worry about our motives as to them the result of our giving is the same. However love is always greater than kindness as it has cost us more to show that kind act.
Peter