sounds like you are doing the best you can for this plant right now..
honestly, you have picked the worst possible time of year to start growing a VFT..because its the dead of winter right now and the plant should be fully dormant..
the fact that is not dormant could cause it some problems later on..
this is what I would do if I were in your shoes..
forget the terrarium.
forget the aquarium.
forget buying any new lights.
you dont WANT the plant to be vigorous and growing right now..its not the right time of year for that.
The plant should be resting right now..
you cant give it a real, cold dormancy because its not prepared for that..sticking it 40 degrees would shock it and kill it.
so you need to give it the best kind of rest you can...its not ideal, but any rest is better IMO that trying to force it artifically back into summer right now.
I would stick the plant in ANY window..dont worry about the light...the light isnt important right now.
the plant shouldnt be growing much anyway.
if you have a cold drafty window, that would be better.
keep a small bit of water in the tray so it doesnt dry out.
leave it alone, except for watching the water level, until April.
In April, put it outdoors, anywhere that gets lots of full direct sunlight.
if it survived the winter, it will come back to life and start putting out new growth..
if not...well, it happens to all of us!
just start over, in april (best time of year to start) with some new VFTs..
but I suspect the plant will probably live..
then keep the plant outdoors until October, by which time you will already know what you are going to do about VFT dormancy for next winter..for your 5 VFTs and 3 Sarracenia you will have by then!
and you will also need to stop thinking in terms of days, and start thinking in terms of cyclical years..but that takes awhile...individual days are meaningless in the life and care of VFTs..
IMO, VFT's and Sarracenia should never be grown in terrariums..
the climate inside a terrarium is just all-wrong for them..
the climate is fine for a few months...but VFTs and Sarrs need very different climates at different times of year..
keeping VFTs in a terrarum is the same as trying to grow maple tree seedlings in a terrarium..
you can replicate June - August ok in a terrarium..sunny and warm..but what about the other 9 months of the year?
Maple trees need a cool spring, a gradually warmer and sunnier summer, a gradually cooler and darker autumn, then a cold and dark winter to be fully dormant.
so do VFTs..
its not an option..its a necessity.
If you grow a maple tree indoors, it will die within a year...the non-changing environment of a terrarium will also eventually kill a VFT.
VFTs need it warm and REALLY sunny in the summer..DIRECT sunlight..
where can you find that? outdoors in the summer!
Nature provides the perfect light for free..
then you need gradually decreasing photoperiod and gradually decreasing temps from summer into autumn..
where can you find that? outdoors..again nature does all the work for us.
The only tricky season for those of us in the Northern states is the winter..Spring, Summer and Autumn are a breeze..just keep the plants outdoors April - October.
but the plants need a COOL winter..the winter of South Carolina..
but winters in the northern states are too severe and will kill them if the plants are left outdoors..
there is a ton written in this forum about winter dormancy..
you have 10 months to read up on that before you have to pick a method.