Please help! Custom BTS enclosure, issue with sealant scent.

[Breadlord]

Hey Everyone,

I'm new to the forums so hopefully this is posted in the right place.

Over this past year I've been working on building a new enclosure for my Indo Blue Tongued Skink.
This project has taken a lot of time due to my only working space being our condo's balcony, and because of that, the frequent need to put a tarp over the project to protect it from bad weather. I live in Ontario, Canada by the way.

The enclosure itself is 4'x2'x2', made from MDF board that was glued and screwed together.
After the build was complete, I sanded it down and then painted it with 3 coats of Valspar Kitchen & Bath Interior. This is an acrylic paint+primer that is water-based, supposedly low VOC, and has the added bonus of being more moisture protected and mold/mildew resistant.
When that was dried and cured for over a week, I moved on to sealing the interior (for additional moisture resistance) with a water-based Polyurethane. I've seen and read about many people using Polyurethane on an enclosure or a custom hide. My first pick was Varathane Crystal Clear water-based wood finish, but at the time my local hardware store only carried Varathane Triple Thick One Coat Clear Finish (red can). After confirming that the Triple Thick was water-based poly, I decided to purchase and continue my project hoping that the thickness would provide additional protection. I followed the products drying and recoating times and even though it said it it should only requires one coat, it also mentioned instructions for additional coats, so I decided to do 2 on the inner walls and three on the bottom/seams as well as slightly up each wall about 3".

Now here is the main issue.
Initially the Varathane had a strong smell, similar to dry oats, grains, nuts or almonds. It spent about 2 weeks outside on our balcony in the later months of the summer, and sometime it got direct sunlight during the day. After it had seemingly cured, was hard to the touch and didn't smell, I wiped it down with a damp towel, some gentle cleaner, and brought it inside to continue the assembly.
However when I placed the glass/acrylic panel doors, closed it up and left it overnight, I was surprised to find that in the morning a strong smell had returned to the inside. It smelt musty, almost like mothballs.
Since I was worried about VOCs and we have 2 cats I moved it back outside and gave it more time to cure.
It then sat outside for another 4 weeks with a fan propped up inside that I would periodically turn on to air it out. While it was out there it had to be partially covered with a tarp so that rain would not fall inside of it (late summer weather moving into fall). After that I brought it back inside, went through the process of washing it again and did another overnight test. The scent was still there.

It's been 3+ months since it was last outside. I've tried having a fan blow on it day and night for a while. I've tried putting activated charcoal, baking soda, or a bowl of vinegar inside of it on multiple occasions to try and absorb the scent. Nothing has worked and it still has a faint musty scent that becomes prominent if left closed and opened again.
About 3 weeks ago, I called Varathane/Rust-oleum directly and talked to one of their product support specialists. I was told that 1; the product is indeed water-based and the oders shouldn't be toxic, 2; that the product needs 21 days at a warm temperature to cure properly, they suggested using a space heater to help it out, and 3; they wondered if maybe the finish absorbed some moisture while drying outside and has mold/mildew growing that is producing the musty scent.
I tried doing this manually with a hairdryer, combing back and forth slowly as to heated up until I was able to get a space heater. I tried leaving a space heater inside of it for hours on multiple occasions (while checking every 15minutes) in an attempt to heat the inside back up to the curing temperature and beyond (23*c -32*c). It got quite hot inside and because the heat gathered around the roof of it, I had to flip it over every now and then to make sure each surface had time in the hottest spot.

At this point I am super exhausted by trying to troubleshoot things and my partner is definitely irritated with the tank taking up so much space in our small condo while I ponder what to do... but I've put so much time, effort, and money into this project that I don't want to give up on it.
This is why I'd appreciate anyone on the forum's advice based off their own experiences or knowledge of reptiles and products used to make enclosures.

I could try cleaning it with a diluted bleach solution?
I could try putting on another product like the Varathane Crystal Clear water-based finish (the one that I initially meant to use and am now using on a custom hide that's curing and smelling fine) if it would seal the scent from the previous finish underneath?
Or I could ignore the scent, prepare the new bedding, fill the tank, smell it again and then move my Bluey into it, but I am paranoid that if something harmful is being released that even if it's covered up by the scent of reptile bedding it could still lead to my baby developing some sort of respiratory issue. For this I may need further reassurance that this situation is actually safe.

I really appreciate any feedback!
Thanks for reading this far,
~ Day