So, I played it and I have to say that it is not very well written
There are almost no interactive choices you can make and the suspects just tell you their stories, sometimes even triggered by strange events. I think Murder Mystery is very intense on writing and you have to give a reason why some people cannot have been the murderers. In the end you just know more about 2 of the suspects, but that does not mean that you have any evidence against them. You should at least give reason as to why the others could not have been the murderers.
To give you an example of what I mean: Assume the wife and brother were not the murderers, then they could still lie, because they have an affair and spent the time together in, say, the shed. Then you have to discover that to exclude them from the list of suspects. This would be a reasonable way of striking suspects off the list. However, this is something that shouldn't be unveiled by itself. Rather by long talks that ask something of the detective.
Sorry, but I think that Murder Mysteries are rather hard to write, because you have to provide a vast amount of possible conversations and you also have to make a sensible story.
I don't find it very sensible, for example, that he was able to climb out of the window, but she didn't have enough time to do so; yet she has enough time to be found in a state of shock near her husband (where she would have had to movebefore, etc.) If you want to hint that, then the Butler should have said something the like. I'm sorry, but I think that the murder and the stories of the others have to written very precisely and then it is still a hell of a job to get the dialogues. But otherwise Murder Mystery doesn't make much sense. In your case, all basically comes down to trial and error to find the proper suspects.

There are almost no interactive choices you can make and the suspects just tell you their stories, sometimes even triggered by strange events. I think Murder Mystery is very intense on writing and you have to give a reason why some people cannot have been the murderers. In the end you just know more about 2 of the suspects, but that does not mean that you have any evidence against them. You should at least give reason as to why the others could not have been the murderers.
To give you an example of what I mean: Assume the wife and brother were not the murderers, then they could still lie, because they have an affair and spent the time together in, say, the shed. Then you have to discover that to exclude them from the list of suspects. This would be a reasonable way of striking suspects off the list. However, this is something that shouldn't be unveiled by itself. Rather by long talks that ask something of the detective.
Sorry, but I think that Murder Mysteries are rather hard to write, because you have to provide a vast amount of possible conversations and you also have to make a sensible story.
I don't find it very sensible, for example, that he was able to climb out of the window, but she didn't have enough time to do so; yet she has enough time to be found in a state of shock near her husband (where she would have had to movebefore, etc.) If you want to hint that, then the Butler should have said something the like. I'm sorry, but I think that the murder and the stories of the others have to written very precisely and then it is still a hell of a job to get the dialogues. But otherwise Murder Mystery doesn't make much sense. In your case, all basically comes down to trial and error to find the proper suspects.