Yo AD! I'm way too late to get in on the chicken or the egg deal. Is it more important to record something that sounds bad, or to make it sound good first? I appreciate the value of a good room and monitors, I do so much field recording that I often have to deal with less than desirable acoustic spaces. If we started out knowing that we were committed to building a top notch studio, we would probably deal with the room first, but mostly we don't. Yeah, I heard the birds chirping too, and sometimes I really miss those windows! They're gone. Now, I can't hear someone start a Harley in my driveway. You can't hear a heavy metal drum kit with the big toms and heavy sticks three feet from my house! That is so damned useful. Frankly, I did some of the room modifications before I even started, and much more later.
If you live in Japan, and all you have coming in your window is bird songs, you are very lucky. And you need better cats. You'll do fine. You've listened to everybody's advice, taken it all in stride, and tried to see everybody's point of view. My only real advice- you've invested some effort and some money in being able to do that demo with real acoustic sound in real acoustic space. Guitar and vocals, and you want to add the other instruments at a professional studio? Works for me. Drum samples or drum machines are good to keep your rhythm honest when you are tracking guide tracks. Then delete that scratch track and get a human drummer! You are in a country with some of the finest percussionists in the world. Want a better demo? Find a human. You've got enough to learn about recording sound with a computer to keep you busy for a while. I believe that combining sound made by a computer with sound made by a human usually sucks. That's just my opinion. Find a human that plays drums. I'd be looking for a traditionalist, to take advantage of that old folk sound of Dai Nihon.
It's also somewhat easier to learn to record hand drums in the beginning, as they don't require the ton of mics and cables often used on a trap set.
-Richie