Are there any dangerous interactions between neurontin, (gabapentin) tramadol, and amitriptyline?

Yes. Theoretically this combination may result in mental slowing and other related central nervous system effects. Again, in theory, concomitant use of Amitriptyline and teamadol may cause seizures and so-called serotoninergic syndrome. However, if you take the medications and have no side effects, no other actions but monitoring is required.
Yes. Yes. The potential exists. Caution is advised. Check with the prescribing physician.