440 timing

My impression is that cam and compression will make it a little soggy. You can add initial to help that. I'd go right up to 20° as long as the starter will turn it. Just remember to back the centrifical back down so total remains at 36°. You may want to read up on tuning a Dominator too. "it throws things out of whack" is more a case of needing to tune that carb. The up side is - everything is tunable on it. You just need to know how.
And yes - my impression is that dyno is screwed up. I hope they didnt charge you for it.