Hey, I had a quick run around your map, and I've got a few things to say about it. First of all it's a great attempt for your first map. But it has a few problems.
1. The cap point times are way to long, you should probably shorten them a lot.
2. There is only one main route to everything (with exception to the cable cars), In all good maps, there are many routes. Take for example 2_fort, you've got the sewers, the bridge and the roof. and in the base, there is 2 ways to the intel.
3. The last point is quite annoying... You shouldn't punish players if they aren't as skilled as someone else, and the stairs out of the water as almost impossible to get up, it took me about 7 tries. Linking to the last point, there should also be more than one way to the point. Something like this is what would cause players to quit your map.
4. The second point is way to close to the re-spawn, and you have to get through it to get to the final point (from what I can see anyway). If the enemy takes the second last point, it's impossible to get to the final one to defend, and it's only a matter of time before the player makes it across the platforms. Along the routes is also quite difficult as you could have a sentry behind each petition making it almost impossible to proceed. You should create natural barriers that stop the line of fire yet allow progress
5. You can see all the way from the second point, through the middle point, and into the 4th. That is way to much of a line of fire, and the points are to close. You need to create barriers and make it not just a straight line all the way through
6. It's quicker to run across than use the cable car
7. The cable car is way to far out of the way, it's just to much of a bother. And if you send both cable cars over, there is no way to get it back, they are essentially an ineffective and useless part of the map, and unfortunately, despite being a good idea, would never get used.
8. The walkways, staircases and ramps are way to thin, a pyro would dominate at these parts of the map, and a spy would be absolutely useless. When making your maps, try to make them cater for all classes not giving one to much of an advantage, and not giving one to much of a disadvantage
Despite all of this, I think there are still some good parts of the map. You have some pretty neat ideas, and the detailing is terrific. The pictures don't give a good look at the map, it actually isn't to dark and despite most tf2 maps that are dark not looking good, you've given it a pretty good atmosphere. I'm not trying to put you or your map down, just trying to give you some constructive criticism so you can make your future maps better. Probably the main problem is your layout. If you look at some of valves maps, you hopefully might get a bit of a better idea.
And sorry for making you read this essay, I just needed to get across some issues and bugs.
EDIT: oh and in regards to starting over, unfortunately, it's probably a bit difficult to fix it, but I would take some of the good parts of the map and put them together in a new part