Like others, I let food help me. Is there a low carb treat that Kramer absolutely loves? You could possibly give him his shot while eating a special treat. Have you tried freeze dried chicken? I have never seen a cat that didn't go crazy for freeze dried chicken.
My girl is a lovebug also but quite fractious, and I could not do her injections any other way. I call it "chicken and a shot"
When she was first diagnosed, I never thought I would be able to get the shots into her. The first week was horrible, I was like you, chasing her around, trying to find a good time, place to do it, and every time I touched her to would swat at me, scream and run off. Add the anxiety never giving injections before and unsure if I was even doing it right...oh what mess! You can practice the injecting to make yourself a bit quicker and more comfortable with that aspect of it (I used a stuffed animal)
I managed Katie's 2x daily injection (by myself) with this routine- About 20 minutes after her meal, I announced it's time for "chicken and a shot".
I prepare the shot, crumble up freeze dried chicken on a plate and set it on the counter (our "shot spot). WHILE she was eating her treat, I did the injection.
It became a routine and she expected it.
I always chose the same shot for shooting, and don't chase her around. On the rare occasion she refused to get up to the "shot spot", I placed her there and immediately give her the chicken and shot. Most of the time she waited in the "shot spot" for it. I think having a "shot spot" (giving the shot in one place of the house w/treat) all the time is better. They begin to learn that's the only place it happens and they get a treat, and they aren't fearful of you every time you get them near in between shots. If you inject them in random spots, they never when to expect it and become fearful. It becomes an unpleasant experience. You want it to be pleasant, and the treat makes it a much happier experience...a reward of sorts.
Hope this helps. Try using a treat he absolutely loves and cannot resist.