Update on Theo: It's been about 10 days since we started the clomipramine. It's been very difficult to administer, so I estimate we are getting between 50-75% of the prescribed dose in him every day. My husband has some success with the tuna flavored suspension: quick scruff and inject directly into the side of his mouth via syringe. We also got a prescription of oral tablets, which I have been cutting in half and trying to hide in his food. (This has been less successful).
Despite these challenges, we have noticed a change in his behavior. The evening rampages are much less frequent. Last night he had only one! My husband put him on a long timeout (20min), and he was calm afterwards. Such a huge difference from a few weeks ago! Thanks everyone for your comments and suggestions