The angelfish, red tailed black shark, bala sharks, twig catfish and bengal loaches will grow too big and active for the tank. The barbs and danio's need to be in larger groups (they are shoaling fish), as do the loaches though. You have too many mollies but the neons are fine.
Are you planning on getting a larger tank and if so, how soon and how large a tank are you getting? Depending on whether you are getting a larger tank soon or not, you should definitely rehome some of the fish i'm afraid, and increase or reduce the numbers of certain others.
My babrs and danios tend to school together and i used to only have 5 mollies, hence the addition of the angelfish to remove fry. I doubt i'll be upgrading anytime soon but all fish have been together happily for nearly two months with no notable problems. I will probably rehome the bala soon. I find the twig catfish very good as it does not dart around tank knocking over plants etc like previous plec i have had so will probably keep him/her.
How would i notice that my tank is suffering from to high a number of fish
The only reason why the barbs and danio's are shoaling together is because they feel they have no other choice, and this is not ideal since it is a sign of discomfort if they are doing this often, increase their numbers to 6 each and reduce the amount of other fish in the tank and you will start to see much healthier more natural/normal behavior in each fish species
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Both the loaches species are sociable with their own kind and will suffer being kept singularly, they should really be kept in groups of 5+ each, however the tank doesn't have the space for a group of Bengal loaches since they grow to large and active for a tank such as yours- the zebra's should be fine though having their numbers increased to proper levels, however you should rehome the unsuitable fish for the tank first as i can image that the filtration is probably already getting a bit strained with the large bioload of the tank.
The angelfish and RTBS will not get along as the RTBS matures- the shark might be alright for now while it is small, but it will start to become territorial and aggressive as it grows larger and matures, and the angelfish will make a likely target for it since the angelfish is unlikely to back down in any dispute with the RTBS but neither is it fast enough or agile enough to out-swim it. The Shark has the potential to outgrow the tank, although might not necessarily do so- however there is a good chance that it will pick on certain other fish in the tank as it grows, it depends on the personality of the shark, so you should keep an eye on it and rehome it if it shows any sign of very aggressive/territorial behavior, since onces it starts behaving that way it is very unlikely that it will get any better.
If your mollys are breeding out of control, the best idea would be to cull any fry that you do not want- either that, or see if you can rehome the extra mollys at your local fish store or on the forum etc.
Based on the actual dimensions of the tank, i would actually say now that you could get away with the twig catfish. Personally, if i had your tank and fish stocking, i would advise changing it to look more like this;
8 neon tetras
6 leopard danios
6 odesa barbs
5 zebra loaches
6 guppys (2 male 4 female)
4 mollys (1 male 3 female)
1 twig catfish
And rehome the bala shark, angelfish, RTBS, Bengal loach and some of the mollys, guppys and neons
. The fish will display much better colors and behavior once you sort the tanks stocking out for the fishes benefit- if you think they look good now, they will look even better once you have the tanks stocking more ideal for the fishes sake (another plus is that the tank will stay cleaner and the fish will be less likely to suffer health problems etc)
. For example, zebra loaches display great behavior when kept in proper size groups in tanks with stocking more suited to their needs- a single zebra loach on its own cannot shine etc.
. With the shark it really varies a lot as to when they start to become less sociable- when i got mine i adopted it of a friend and it had already become quite territorial at about 3-4inches long. But with other people have heard their RTBS getting territorial at 5inches or even 2icnhes long- so it really varies a lot, RTBS's individual personalities can vary a great deal. While not all RTBS become territorial towards other fish, most do at some point- the level of aggression can vary massively though, some will go for pretty much every fish in the tank, while others will only target fish which have similar coloring or patterning to the RTBS, or will only target slow moving fish or fish which like the same space/habitat in the tank as what the RTBS likes etc. 
) if you have the time- remember that there is also a buy/sell/swap section on the forum too if you want to try it out 
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