A couple of suggestions
I think preferred type of serves would be 1. top/slice where you toss the ball a bit in front and swing 8 to 2 o'c rather than flat serve, 2. Kick as you need a good 2nd serve, and 3. flat. You had flat as the 1st in the sequence. I am not a bit fan of "flat" serves because unless you are very, very tall there is no margin of error and it pretty much a worthless serve. Isner, Federer, and Sampras all have high RPM numbers on their typical 1st serve. So, the power top/slice is the "money" serve in my view and should be the one you work on first.
Another thought is if you use just hips and shoulder rotation without any or much leg input, you really cannot toss the ball too far in front. I have a friend who serves like this and he has a fairly decent serve - he serves with very little leg motion almost from a stable base. But, as an alternative, you can try a step in serve like Boris Becker hit. Basically, he walked into the serve with his R leg as he rotated the shoulders into the hit. Your R foot will end up about .5 to 1 foot length in front of you lead L foot. This will also allow you to place the toss about a foot out front for the top/slice serve.
Personally, I would do the fix feet "lazy" serve as a drill and then use the step in serve as my actual serve. Then, work on more knee bend and more push up from the legs.