I do not want to add anything to what the more accomplished photographers have already told you about your portfolio, and I think you have got some very good advice in this thread. I just would like to say that if you are hell bent to "achieve impossible" again, in my opinion, you have to adopt a completely different approach to what you have at the moment. Your portfolio looks way too casual. You have to be much more systematic and conscious of what you are doing.
First of all - I think self education is not enough here because at best it is a very long and winding road. There are extremely talented self educated photographers, of course, but this kind of talent is rare and and it shows if not immediatly, but early.
So if you have the money, invest in your education and do it wisely, work as an event photographer or anywhere in photography where you can earn money, it will add to your technical pedigree anyway.
Secondly - a landscape photographer is a very broad term, you need to find your niche within landscape photography to be able to market it succesfully. Who will be your customer - housewives decorating their houses? Media editors?
Then you will need to find your own style accordingly, work on developing, improving and polishing it, making it recognisable. What exactly is going to make it unique - your compositions, your feeling of colors, your locations, your inique shhoting technique, your post production prowess... I have no idea whatsoever. There you will need a professional help, that's why a formal education or a good tutor is so useful. But anyway only you will make it. You will have to put your own mark on these frigging sunsets or whatever you choose to shoot. So that people would say "Is it John Gannon sunset?" THEN you can build a powerful portfolio and after that MAYBE, just maybe you will have a chance to even sell something

. I can only guess here, but my feeling is, as other guys said, it is about as difficult as flying to the moon. But if you were in Air Force, than maybe..
In the meantime - analyse work of the best landscape photographers, ask yourself why this image is so good, and you have to consistently come up with the right answers. Because talent is not something abstract, it is just a simple ability to see things, tell a good image from a great one, break it to pieces and come up with right conclusions. You need to get under the skin of your favourite photographers and understand how do they do it and how do they see the world around them, what motivates them aestetically etc etc. copycat them mercilessly to learn - not to borrow their style, but to find your own. Because you have to face the truth, if you want to be a sussessful landscape photographer, these guys are your competition. Can you do a landscape exactly as they did? Do you see how to improve upon it? Tough, really tough..
Just my 2 cents into your future bank account. So good luck !!