when to do my first Ironman

Hi,
I really enjoy reading this board. There's so much valuable information here.
Here's my background:
-26 years old
-this is my 4th triathlon season (no major background in sport before that)
-so far I've been doing mostly short distance triathlons
-my PBs are 15:56 for 5k run, and around 20 minutes for 1500m swim
-raced my first longer distance race this weekend in Austria and finished 45th (26:20 swim, 2:29 bike, 1:19 run). I'm not too happy with this race as I expected much more. I lost big opportunity on the bike when I let the big group go, and my run was not as good as I planned (I was confident that I could run sub 3:40 min/km). I was also the only person in PRO category without TT bike and aero wheels.
-as I've been focusing on shorter races, I don't have a lot km's on the bike. Now I'll probably switch focus to long distance, so that will have to change.
-I have full time job, but I manage to collect up to 28h of training weekly

I would really like to live the life of pro triathlete one day. I assume I have better chances in long distance. I would have to swim sub 17 min to be competitive in shorter races and I don't know if it's possible. Also I have a diesel engine, and I think I'm much more suited to longer races.
So, my question is:
When to do my first Ironman? Should I do half Ironmans for another couple of years or jump to full distance next year?
Thank you
Andrej