Planning stage 1 of detached Garage buildout

Hey everyone, I've already spent a great deal of time on here geting some of the basics down. I have a pretty good handle on the basics, I just (like everybody who does this) need some guidance on a few measures. I am a producer and songwriter who works primarily in advertising and record production. Like i said in the posting title, this will be stage 1 in hopefully a two stage buildout. The garage is huge ( a major reason for buying this house) I work at a studio that i pay rent for......basically im sick of that, and want to put my real estate to good use. The garage is basically split in two. A large two car bay, and a workshop side with storage loft above it. each side is 20*30. the bay side is huge wide open (future tracking room, ie stage 2) and the workshop has a drop cieling height of 8'4 and up to the rafters above is 9ft. above this is a storage loft that looks out to the garage side when up there. there is a staircase that leads to this loft, which i intend to remove and replace on the other side. This way i can seal the entire workshop side off from everything else. the floor is a concrete slab which i intend to put oak down on. I want to make a nice big room that is acoustically great with a booth (either custom or pre-fab), so I can blast drums at 2 am if possible. I would love for the room to be a large track/control setup. I really dont want to get into floating floors and decoupling 2 seperate rooms. But I have neighbors, so my first planning proprity is to make sure my neighbors dont complain. I have a few questions regarding this there is a 3inch spot on the current footing to accept a new wall frame. My idea was to build my heavy duty (3 layers of 5/8, rockwool, caulk) wall, on this and bring the face down flush with the floor. /Users/taylormclam/Desktop/important stuff/CL/footing.jpg quest1- should i remove the current wallboard and replace all the pink stuff with rock wool. then re-rock, then build my wall? Or can i just add a layer or two of rock to it. I was hoping to get away with destructing as little as possible. My neighbor is about 40 ft off the back of my garage in a quiet neighborhood. Most of my music is made during the day, however, I want freedom...... quest2_ would it be feasible (cost?) to build some kind of masonary wall behind my garage, up against the exsisting siding, or would it be easier to treat inside. quest 3- Since the acoustic drop cieling is kind of chinsy, plus all the flourecents need to come out, Im thinking of rockwool in the upper rafters, followed by layers of rock, then if necc, drop cieling from there. does this sound adequate? Quest4_ I took down the gas fired shop heater that was in there, and was thinking fof replacing it with a mini split system by LG......looks like a picture frame? anyone use this.......? like it? It does heat ,ac, and dehumidifies....seems great. although im not crazy about electric heat for my bill, but i figure its gonna be insulated like crazy so hopefully it wont work that hard. Quest 5- My front doors open out, I was considering constructing a second set on the inside that opens in,,,,,,,other wise, I would need to invest in some serious steel commercial jobs, which I'm trying to keep out of my budget. ......which is btw hopefully around 15-18k I wanna do all the gorilla work myself except the floor. well I guess thats it for now. I included pics of the setup. I cant wait to start but know that planning is everything. I have so many other questions regarding acoustical stuff and others, but wanted to start with the meat. I will be doing a sketchup once i get a feel for the technique. I have incl

sorry about that this is view from garage side, and view as you walk in through the double doors.