Have I messed up? (Backer Rod and Caulking phase)

Hi, I am currently building my small drum practice room of staggered-stud construction with two layers of 15mm Soundcheck with GG. I think I have messed up and not sure how to fix. Please bear in mind that I am not an expert in construction, and have very limited funds. I'm just trying to get this built to the best of my limited ability and budget. The existing small concrete slab that I am building my wooden struction on, did not have a damp proof membrane, so in an attemp to stop any rising damp down the line, I covered the top of the slab with a Damp Proof Membrane before commencing with building. Here is a photo of where I am currently, and a picture that shows the construction method. I have the two layers of soundcheck up, and am currently plastering accross all surfaces to get a nice finish and to also fill the joins and screwholes (I'm doing this instead of tape+mud). The Weird rumpled blue floor is the DampProof Membrane that I have laid down on top of the slab. Now, I was intending to lay 18mm OSB down on top of the DampProof Membrane and on top of that, laminate flooring, with a wooden skirting-board around the premiter. Here is a picture of how I was intending to construct this, with the use of acoustic Caulk and Backer Rod. Now, is the Damp-proof membrane (and the fact that its all rumped as I couldn't get it to lay completly flat, gonna cause the acoustic caulk seals to break in time? Will the second Backer-Rod and Caulk around the perimeter of the 18mm OSB be okay? I was worried that I have messed up and by using 13mm BackerRod (in a 9mm Gap) I'm going to destroy my sound isolation? Will the sound just flank through the 18mm OSB, and then pass through the failing caulk under the walls? I have enough spare drywall that I could place two layers of 15mm under the 18mm to beef up the floor, but I was worried that they might crumble over time (even with the 18mm OSB over them) or that if any damp gets through the floor, it will cause them to degrade etc. Am I best off putting them under the OSB, or just leaving them out ? If anyone has any pointers over how I should procede, I would be most greatful! Many thanks/ Steeve

"Now, is the Damp-proof membrane (and the fact that its all rumped as I couldn't get it to lay completly flat, gonna cause the acoustic caulk seals to break in time? Will the second Backer-Rod and Caulk around the perimeter of the 18mm OSB be okay?" Depends. Is the damp proof membrane run up the wall structure or does the wall sit on top of the barrier? As long as the top side of the barrier stays dry the caulk should remain effective. But if this membrane is terminated in some way, or cut short, in such a way that if there is moisture buildup underneath the barrier (on top of the concrete) then it will most likely seep out to the edges of the barrier...that is where the problems with this type of procedure will begin. If the leakage moves to the edge of the barrier and at the edges is where your caulk and backer rod is then it [moisture] could very well reduce the effectiveness of the caulking. There may be an issue with mold/smells and rot depending on the installation methods you used and how much attention was given to what is happening under this barrier.