Hello,
First of all, sorry for my poor English.
Please find bellow the list of what I am growing and I am sure of the hardiness:
. Basjoo varieties, hybrids, fancy commercial names (all that I could find in France): Var. basjoo, "freddi banani", var. sakhalin, var. sapporo, var. tchetchenia, "x hybridum".
. Sikkimensis: var. sikkimensis, var. red tiger
. Helen's hybrid
The others species that I grow, are outside for 1 to 3 seasons, with sweat winters. This is not enough to make a conclusion about the hardiness.
Concerning the winter protection, you can find the details in the article that I wrote recently for the magazine of my gardener's association:
http://actus.societe-francaise-accli....fr/2019-2.pdf
It is written by French, but you can understand from the pictures. You may also translate the interesting chapters with Google.
Concerning your Ensete ventricosum, congratulation! In sounds very fast growing.
Yes, it is dying after flowering. You can cut the pseudostem very short, at the ground level, and it will make plenty of pups. Ensete are not making pups during their life.
I guess your ensete is planted outside, for a so fast development. If so, bring it indoors, because it has no chance to survive a winter in zone 7a, even with my heavy protection style.
Alternatively, you can find on Youtube, the method for producing new plants from the meristem cut in small pieces.
Hoping this helps.