It is best to plan a tank from the start, house the fish from the start in a tank that they will be able to live their adult lives in. Done this way you can also get fish that have similar requirements, this is the big issue for me with this tank right now, you essentially have 2 groups of fish that might work ok for a couple of months but one or both groups are going to be suffering in the long term - as we have seen with the death of a ram.
When you mention pushing the limits each of the groups I would suggest are arguably pushing the limit, what you have at the moment is a bit of a ticking time bomb. I'm speaking from experience here, I've tried combos like you have here, I didnt listen to people and thought I knew what I was doing and I made the mistakes I would predict you will in a the future and the mistakes I think you are making now. I would really make a choice on this tank and if you are open to rehoming some fish like you mentioned you can 'fix' this tank.
When I say you have 2 groups of fish these are the groups
Group 1
2x Convict
2x Jack Dempsey
6x tiger barb
1 x red tail shark
Group 2
2x electric blue acara
3x angelfish
1 x leopard pleco
1x German Ram - I would just rehome this fish, as Bub pointed out it is not a Bolivian it is a German Blue. The needs of this fish are very specifc and you wont be able to meet these and those of the other fish in the same tank. You could consider setting up a 20g long or a 29-30g for it and build a specifc community around it though?
At 7.5 German I think that works out as 134ppm which would mean you have quite soft water (
@essjay is that right?) If so group 2 would be the way to go and you would be able to add other fish to the tank like characins, catfish maybe some oddballs - but it would all need to be planned and prepared to work for the lifespan of the fish you choose. I might be wrong with the conversion of the original figure though so would like some clarification before I recommend fully.
Rescuing the pleco is a very noble thing to do and I would agree with you that it is likely stunted. In terms of how best to help it have a good life I would recommend a tank that has a footprint 2x as wide as its length and 6x as long. Your 5 foot might be ok for this as it is close to 6x length but what sort of width do you have?
Wills