Welcome to the ultimate sport, the one you will practice for the rest of your life!
I wish I had found out about surfski.info before I bought my first surfski and made a lot of mistakes.
Don't feel bad about being cautious to venture in open water, even more so if you paddle alone.
When I started, I set myself the goal of reaching a nearby island, 10 km offshore. But I was afraid of being alone in the open sea, so that I approached my goal with baby steps... One day I set to paddle straight away from the beach for only 15 minutes, then another time I paddled a little more, like 20 minutes, and so on. It took me many paddling sessions to reach my goal. But in the process I got used to being alone and far away, got used to the distances and the landscape, learnt some orientation, became sure that I was not prone to feel seasick etc.
Remember, you will be doing this for the rest of your life! There's no need to rush.
Stability and safety first. Add some experience, that will come with many hours of practice. It's good to get coaching and learn proper technique, so you will avoid injuries and paddle more efficiently. Little by little everything will fall into place.
Current: Epic V8 PRO, Think Evo 3
Past: Epic V8, Epic V10 Sport