For a boa, I think your cage is too hot, also humidity is too high. Cool side about 77* is fine, warm side about 86*, basking not over 88-90*. Humidity about 60%.
More vent holes should help. As far as this boa feeling cold, remember that most all snakes feel cold to us because we're 98.6*...& also when we handle some snakes
that need lower temperatures (such as corn snakes) the reason they don't want to sit still is because we're making them too warm & uncomfortable. Sometimes you
need to watch where your snake spends time to see what they like: the BCI I had for many years often liked the cool side (75-78*) but used the basking area & the
UTH-heated hide too...and she remained healthy.