Hi Julie,
The tongue and improvement from going outside (in the winter) suggest a Heat condition, despite the slower heart rate. At this time of night, Heat is located in the Yang Ming, so a formula that clears it from there may be a good idea.
On the other hand, a partial response to TMGTY says that Blood or Yin deficiency is the cause of the seizures, and in that case the dog may be hot all the time, and not just at night. If that is the case, a Yin tonic may help, while continuing the TMGTY. Something like Yi Guan Jian or Zhi Bai Di Huang Wan. Since the seizures are mild, that may be an easy first step.
Otherwise, Yang Ming excesses in the middle of the night are ultimately caused by Jue Yin excesses. The formula to address this dynamic is Wu Mei Wan. We've found for it to work well, we need to add Tian Ma (or perhaps continue the TMGTY), and in addition use Qing Ying Tang. The two formulas, WMW and QYT, have a synergy that allows them to slowly reduce seizure tendency and severity. In a milder case like this, they may stop completely.
One of these two strategies should work. To quickly eliminate seizures altogether while using herbs, you can try using Keppra. It's much superior to PB or KBr, when taking an integrative approach to seizure management, since it works right away and is easier to withdraw. Since this dog is not grand mal in its seizures and is not apparently in danger of status epilepticus, I don't know if you have to go there, though, just yet.
Note that adding in the cooling herbs of ZBDHW, QYT, or WMW should have the long term effect of reducing seizure predisposition (we think, by inhibiting the ability for synchronous neural discharge). So ZBDHW may be a better option than YGJ if you're going to continue the TMGTY approach.
Hope that helps! Let us know how it goes!
Steve