RE studio planning and designing

Hello all! I am planning to build a multimedia studio in a wooden object (workspace/garage) near my house. For months I am thinking how, what to use, how much, price, why, and so on, and after reading this awesome forum, I started to finally draw my plans. Slowly..
 What I want? 
I want to make a decent mix room (audio & video) and a live room for jamming / recording. 
 Where am I? Slovenia/Europe. 
Just behind my house (not connected) me and my father built this garage, where inside (ground level) is a car garage/storage/workspace, and above I would like to make my studio. My first neighbour is 20 feet away. What are my goals? I am working with sound for theatre & movies, I am also making my own electronic/acoustic music. I play percussions, drums, gongs, weird objects, home build instruments, pianos and keyboards. How loud I am? I am not very loud with mixing, so far I’ve been mixing mostly on my headphones, during the night (not very good idea!!!) When I play drums, (not often) I am loud as average drummer. Mostly I will play alone, upper piano, percussions and keyboard stuff. I care for sound not going out through my walls and celling too much, but don’t care going up and down in my garage. ..Not possible....) Current walls, floor and ceiling: Walls- I just have one layer of wood on the outside (8”x3/4”), nailed on construction studs. (see pics) 
 The celling - also wood nailed on studs, above is roof. The floor: wood - insulation - wood, nailed on the same stud. 
 Dimensions: 
Control Room: 2.4m high (8 feet) , 4.9m long (16), 4m wide (13) 
 Live/recording room: 2.4m high (8 feet) , 9m long (29,5), 4m wide (13) Basic idea: First I would like to design a CR and LIVE room. I have problems with a hight of this place (2.3m), and inclined celling (starting at 1.3m) on each side of the building. When I will make good design, I will start with resolving wood cracks in all of my outer walls. I will put 2 layers of wood (I already have lots of (6x1) and then 1 x drywall attached over. All from inside. 
 Then I will put separate stud construction for inner walls, to shape the studio. Space between walls will be 5 - 10”. In first wall I will put Glass wool, in inner wall Rock wool. 
For the celling I can’t go with 2 walls because of small height, so I will attach RC1 + 2 layers of drywall (maybe with Green Glue between).
 Budget: Don’t have much now, I will build slowly and at minimum costs. Will start at 3000$. Thanks a lot for your help!!!
 Mateo P.S: Sorry for my bad english and even more bad sketchup.. I will try to learn both.

Plans... Please comment on my room design plans! Problem is dropped celling on both sides, starting at 1.3m..

Floor question: How to treat it without loosing too much of a hight? Now construction is wood - studs -wood. I have 2 options.. Attaching massive 1.5'' thick MDF directly on top of existing floor, or floating floor with same MDF on studs + rubber pad + 2" isolation within..