To establish a rapport with the Baptists (Jefferson was a Unitarian , a group closely allied with the feared Congregationalists), Jefferson borrowed from the words of Roger Williams, a prominent Baptist preacher:
"When they have opened a gap in the hedge or wall of separation between the garden of the Church and the wilderness of the world, God hath ever broke down the wall itself, removed the candlestick, and made his garden a wilderness, as at this day. And that there fore if He will eer please to restore His garden and paradise again, it must of necessity be walled in peculiarly unto Himself from the world.."
The "wall" metaphor was one directional. The church was to be protected from incursion from the state not the other way around.
This is made evident by the following:
From Affinities and Animosities: Universalists and Unitarians in the Formative Period :
When, in late 1820 and early 1821, Massachusetts went through the exercise of revising its Constitution, the attempt to separate church and state was opposed successfully by the eloquent Daniel Webster, among others. Channing, and a number of other Unitarian ministers, sided with Webster. In an eloquent sermon in December 1820, titled Religion a Social Principle, Channing defended the union of church and state, arguing that religion is not merely a personal matter between God and human beings: ". . .Therefore, Society ought, through its great organ and representative, which is government, as well as by other methods, to pay homage to God, and express its obligation."
Thomas Jefferson wrote on June 22, 1822:The question arises that if Jefferson's Danbury letter does advocate a separation of church and state as some claim it does, what was Jefferson doing proselytizing for and being in a congregation which opposed such a notion?
"I rejoice that in this blessed country of free inquiry and belief, which has surrendered its conscience to neither kings nor priests, the genuine doctrine of one God is reviving and I trust that there is not a young man now living in the United States who will not die a Unitarian."
Channing was the most prominent Unitarian minister of the day. Jefferson surely knew about the debate which had raged one year before he made the comment above.
I don't think any churches should receive tax money, as your post notes they did in the early 1800s. The fact that Massachusetts churches might have argued to stay on the public dole doesn't make it right or indicate that Jefferson supported that specific action.
Jefferson's Unitarian church may have differed considerably from the Massachusetts Unitarian churches. The three Unitarian churches I've been to in different parts of the country were quite different.
One need only read about the European wars of religion that preceeded the development of our Constitution to see the dangers of state sponsorship of religion. If you didn't belong to the state church, in some places you were in danger of being burned at the stake or prohibited from holding services or having your churches destroyed. Toleration of other religious beliefs or nonbelief was slow in coming and is still hard for some to accept.