I think you may be 'jumping' the gun on the Ultra Sound.
Those number are not very high and I think he may be a tad young for an accurate BAT. Also did he have any flea/tick treatment, how about vaccines or heartworm? These thing may throw the number off a tiny bit
I think you should do the BAT again in a few weeks. I would pass on the U/S right now, they are only 60% accurate (I think). So even if they don't see one there could be one, etc...