No problem for this juniper to live outside all winter. My winter temps are similar to your -5C and my junipers never come indoors.
You are correct but provided it does the job and you are not showing the tree I don't really care how it looks. Practice will help and your wiring should improve over time.
shape of tree was perfect for cascade so I decided to give it a try.
Cascade is actually a hard style to get really good.
When I think of cascade trees I think of mountains and cliff faces where the trees grow out to the light or are forced down with constant wind, snow, etc. Under those conditions it would not be normal for branches to grow in the opposite direction. It is normal for beginners to want 'balance' with branches going in opposite direction but with some styles balance is achieved by making everything move in one direction.
Design of your tree is entirely up to you but if I was doing this tree I would remove the 2 lower left side branches then bend the next 2 top branches to the right to compliment the main cascade trunk. In bonsai less is often better than more.
Consider those factors and see if you agree.