... I didn't touch my front brake....
You gave up about 80% of your stopping power right there. You best brush up on your skills. Your Strom should be able to outbrake any SUV without trouble.
1. Which brake is the most effective?
The front brake is the most effective, giving between 60 & 80% of the bike's stopping power in hard stops, depending upon surface conditions. This is because most of the weight of the bike and rider transfers forward onto the front wheel when the brakes are applied.
A common example of weight transfer is when you trip on a gutter - your feet stop but momentum keeps the top of you going and you fall flat on your face. The weight transfer that takes place under braking on a motorcycle pushes the front wheel onto the ground and makes it grip very well.
2. Is the front wheel likely to skid if you apply the front brake hard?
No. The front wheel is likely to skid uncontrollably and bring you down only if you jam the front brake on hard. If you apply the front brake in a staged (progressive) process, the front wheel may skid but that skid is normally quite controllable.
3. Is the rear wheel likely to skid if you apply the brakes hard?
With most of the weight being on the front wheel, the rear wheel tends to be light under braking and will therefore lock up and skid very easily.
4. How do you control a rear wheel skid?
Control of a rear wheel skid is easy. Just keep your eyes up to the horizon and look where you WANT to go (not necessarily where you are actually going) and the bike will skid in a controllable manner with a minimum of fishtailing.
Basic and advanced braking techniques are best learnt under controlled conditions rather than when a truck pulls out on you! Your local motorcycle school will run a fun braking exercise session for you and some mates if you care to call the school and arrange it.
5. Is braking a natural skill?
Braking, as with any riding skill, is a learned skill, not a natural one. This means you must practice the correct braking skills enough to make them an instinctive reaction before you can be sure that you will do the right things in an emergency. Overseas research has shown that, because of panic overpowering the rider's conscious reactions, nearly a third of all riders do absolutely nothing in an accident situation: they don't even apply the brakes!
If, however, your high level braking skills are so well learnt that they are instinctive, you will do it right, no matter what the situation. However, this requires you to do a lot of high level braking skill practice, the skills will not come with normal everyday riding.