The 30 gallon would be a good place to start getting your mollies bigger MollyGirls. Don't give away the space while you still have a good use for it.
I look at your tank list and it doesn't really look like very much. You have a big tank for some very large fish and the rest are a single 55 and a few small tanks. There is probably lots of space for more or larger tanks if you really decide to get serious about keeping fish.
I keep my community assortment of fish in my 125.
I have a single 55 that I am using to grow out my molly drop of about 30 fry.
My daughter just gave me back my old 60 gallon and its stand but it needs the top brace repaired before I fill it with water.
The 40 long has a breeding colony of Ameca splendens, butterfly goodeids, in it.
I have 2 of the 29 gallon tanks, one holds a failed endler breeding experiment and the other some green goodeids.
Then there are the 4 20 gallon tanks holding a wild endler colony, a pair of killies, a small group of wild green swordtails and in the last one a group of Corydoras hastatus.
There are also the 45 with some of the endler colony, because their 20 became over crowded and the 40 breeder that holds a breeding colony of leopard goodeids.
That is about it for large to medium tanks. There are also the 10 gallon with the Brachyrhaphis roseni in it, the 10 that is holding the Goodea gracilis, the 10 with the Limia perugia, the 10 that holds a small colony of Heterandria formosa, the 10 that holds my wife's guppies, the 10 with the Limia melanogasters, the 5 1/2 that is holding a pair of orange tailed goodeids, Xenotoca eiseni, and finally 2 empty tanks that I expect to fill at a fish auction in 2 weeks.
I may have forgotten one but that is the tanks. Just thought of another container that I use. I have a 150 gallon stock tank set up in the back yard to grow out my fish during the summer. This year it has some Xenotoca eiseni in it but last year I used it to grow my wild green swordtails to adult size. An outdoor tub is the ideal location to grow out young fish because they seem to grow faster and do so much better outdoors than in an aquarium. I don't worry too much about feeding the tub because insects come along all the time and land in the water. They seldom get to fly away again so the fish are almost self feeding. I do feed them 2 or 3 times a week just in case the insects have not been arriving often enough.
I am starting to think that I have may soon have too many tanks but there are still lots of places in my home for more. Most of mine are set up with 2 levels of tank on the same stand so that I don't burn up too much floor space with my tanks.