You have bolted together an pretty odd mix of parts.

The cam will not like to run happily at low rpm but you desire the low rpm for cruising.

Today's answer would be a broader range camshaft profile. Less overlap. Something that will run well, just off idle.

The cruise rpm under stall speed. Again, in a modern car. The answer is a lock up convertor.

I was able to experiment with this with a 518 lock up 4 speed automatic.
My conclusion was the manually engaged lock up was more useful at low rpm. I could engage lock up at 1700 rpm and pull 500 rpm out of it. Lock it up at 2500 and it would only pull 200 rpm out of it. At 3000 rpm, lock up vs no lock up was hardly noticeable.

Try comparing you cruising rpm vs cruising rpm on jack stands. What is the rpm difference? Alot says it's really slipping. None means, I wouldn't worry about it.