I'm sorry I just started reading about poor Tubby.I havn't been on the computer to much because of back pain.Well,
My BooBoo is 16 years old and looks just like your Tubby all black.But my BooBoo has terrible Arthritis in his legs and we use the "Joint Max".It helps bigtime.My KiKi used it before he passed away from Cancer.But he had arthritis too.(BooBoo's brother)And KiKi responded so well to it he was jumping up on the cat shelves for the windows without our help.And BooBoo runs a bit around the house now.He still needs stools everywhere though.Just like KiKi did.We bought them for the beds and anything else they like to jump on.But Joint Max is great.
The only problem with these pills is that they are big.So they are chewable so you can crush it up in their wet food OR what we do is crush it up and add very warm water then when it's all pasty put it in a shringe and do it that way.Apply in their mouth.It doesn't taste bad.
There is a website www.jointmax.com if interested.Otherwise I would just do what your doing because he seems better with the heat and the helping arms carrying to the box now and then.My hubby carries BooBoo downstairs a lot and up too.Poor little guys.They really are like humans in some ways.Just can't take all the meds we take though.Good Luck and Prayers on the way for Tubby.