[(E)]

The first calculation for the 2 gigajoules would have a 30% improvement factor from not using frequencies of light not used by plants. That reduces the demand to 1.5 gigajoules or approximately 17kw per person.

The other 90% number for animals and non food crops etc I set at 40% due to algae farming and plastics for fibre. The TL would maintain longer locally as it was assumed to be a research facility with auto factories. Edit. At 40% you get say 24kw per person.

It also not about maintaining the TL the assumption for ATE is fairly high technological endurance. So for setting specific reasons the TL decline is on the optimistic side.

I would say a TL9 geothermal generator made a bit more power, but as that's sci-fi terrain it is merely speculation, They are by there very nature quite easy to scale up.

The lifespan of the fuel for fission is an issue however, in my thought process I just ticked the box "advance breeder reactor" and made a note about refueling it.

Edit
The ventilation issues would be mitigated by design especially with the ability to use waste heat to generate movement, that waste heat may be useful for sterilization purposes as well. My thinking was the sterilization issues where going to be smaller(not absent) as a result of the bio-system approach. Cold plasma related technologies might also be used for cleaning/sterilizing. I am also speculating about what highly qualified people who are more advanced than me can do. . .
Photosynthesis is about 1-6% effective for energy conversion as well, with crops around 2-3%, again this is discounting any improvements in TL9 genetics. The 30% improvement for controlling the light spectrum could also be plausibly increased to 50% or higher, I just reduced the efficiency for my calculation as a matter of coarse.
Edit the second
If the power generation grates against your plausibility standards, change it for another, subterranean hydroelectric, beamed power from orbit or whatever suits. The beamed power would make a good defensive barrier option to. Power is the limiting factor in this operation and gurps ultratech shys away from specifics.
Edit the third
Sorry about the multiple edits but I am only just looking at this specific angle of analysis, fully tweaked artificial light might do better than 15% efficiency for crops 10% seems quite achievable for TL 9, Natural sugar cane apparently manages 8% efficiency on plain sunlight.