Hi Dragonfly

My heart bleeds for you in this situation. You obviously have the feelings you do because you love your son and grandchildren very much, and who can fault you for that?
I've had people I've wanted to tell off for abusing and using family members I love. One is my dad's ex-girlfriend and the other is the wife of my deceased brother. What I have done is talk to my sister, I've thrown a pillow at my wall and screamed at the top of my lungs when no one is in the house to hear me, and I wrote a letter to my siblings about my dad's ex-girlfriend and what I went through at her expense. My brother (the one who is still with us) is appalled at what I went through, was very supportive, and glad I opened up. I also had a talk one day with my minister about not wanting my dad's ex-girlfriend at my funeral. I went in saying I know I should forgive and worrying about what my minister thought of me, and left feeling justified for my feelings due to my minsters open mindedness. Hoping some of my methods may help you.
I see nothing wrong with you using the term loser. I wouldn't call them that to the grandchildren or anyone who might take offense to it (your son or anyone else you know), but by all means call them that here.
For the swimming it's a great idea to take someone with you who knows how you feel for moral support.
Thinking of you.