Your problem is very easy to understand. A soft light is an extended source, that lights in many directions, while a spot light (fresnel) is a directed source.
When you try to cut a large source, you actually don't realy cut it, it's more like if you would reduce it's surface, then it's luminance.
If you cut a directed light (fresnel), it works because you can have deeper shadows with such sources when you cut them.
this is why cuting large sources is definitlya pain in the ass.
When you work with large sources, large cuting materials, and put them far away from the scene, it's like you're trying to turn this large source into a small one, compared to the set's dimensions.
trying to have a soft light and contrast beetween the foreground and background is a little bit contradictive, somehow.
This is why it is so difficult, and it becomes hardish. Only great dops with help of great gaffers and grips, like Mr Zanit can handle this work.
It's a very satisfing thing if you can get thru with the help he gave. But if you want to spend less time on this, why don't you try to go on with sources that may give the work easier ?
One consideration about the set is also that if you have the background as far as possible from the comedians, it would be of great help (it helps you to set counter lights, as well, if desired).
If you light the major part of the scene with fresnel lights, even with diffusion on their barndoors, you might get a stronger contrast beetween backgroug and foreground, as you will be able to cut them easier, and if you want the light to be kinda soft on the comedians, well, put the sources that especially light them as close as possible from the camera axis for non moving shots.
A nice device to have a soft light on the comedians while having contrast beetween foreground and background if you have a tracking shot, is to put a "basher lamp" on the camera or dolly in the camera axis, wich is a small soft light that will always remain in the axis. Doesn't work all the time, but sometimes does (mind it's not too strong as we don't "feel" it).
(my idea was only to be quick with soft light on the comedians, and contrast beetween background and foreground, with ability of cuting the set keylight)