Scanning through your link, the first thing I noticed was about Otos. They won`t touch BBA. What they will do is clear up brown diatoms and possibly the green covering that can appear on hardscape.
My only experience of BBA was an issue I had with CO2, something I think that this type of algae is closely related to. Once it is established it is very hardy, and correcting the original problem may not shift it. Fortunately, dosing Flourish Excel can be very effective at killing it. The way I used it was to switch the filter off, remove 50% of the water and, using a small syringe, spot treat the areas of BBA as per the dosing levels on the bottle. Leave it for a minute or two, then top up the tank and switch the filter back on. Excel is an organic form of carbon for your plants, so they will benefit from it, too.
As for the poor CO2, it is hard to pinpoint on a tank without CO2 injection, but it will be down to either very low levels, or fluctuations in levels. Adding Excel to a low light tank, which I am assuming yours is, should cure the BBA. The tall, grassy looking plant you have is a type of Vallisneria sp, which I have read can melt when Excel is used, so just be aware of that possibility.
The green stuff on the glass you are experiencing is something I get every time I set up a new tank. What I do is let it build up over a period of a few weeks. Two of my tanks got to the point where I couldn`t see through the glass, and the algae had a jelly like texture. It is at this point that it should start to disappear. Once there is about 25% of it remaining, I tend to get fed up with the messy look and clear it all off. I still have to clean the front glass every couple of weeks or so, but what does appear is minimal and the glass on all my tanks stay pretty much clear all the time.
To clean it off, I usually use a plain kitchen type of kitchen roll, which I wipe over the glass when the water level is low during a water change.
People in your link seem to be telling you to give up on the small tank, but I don`t think that is really the right attitude. I have a 24l tank which is less stable than my bigger tanks, but I wouldn`t say it was difficult to keep. If poor water quality is an issue, and your fish are dying, keep up with regular water changes. Don`t be afraid to carry out 50% water changes if necessary. My bigger tanks get a 50% change once a week, and my 24l gets around two a week, although I am looking to reduce this as it is getting on my nerves. Water changes are also useful in combatting algae issues, as you are taking out algae spores with every change.
Dave.