Is there something inherently wrong with being small, or not having Sunday School, or not supporting the modern missionary movement?
I only named these things as a clue as to whether this man came from a Primitive Baptist background. If you had heard from him any of these qualities of the "small" church he had attended.
This being related to the question as to the doctrine of hell and that there are some Primitive Baptists "no-hellers".
As far as I know these are the only Trinitarian Universalists that I know of except for a church in Boston in the 18th century.
Apart from all that, these are subjective questions, the answers depend upon how you view the Scriptures concerning each.
I'll give my answers apart from the Baptist Distinctives.
I believe the question concerning "small" would be answered with a "no" by almost everyone including myself. I would say no there is nothing wrong with "small" from the Scriptures. Personally after having been involved with both small and big, I prefer "small". In addition what is "small" to one may be "big" to another and vice versa. Small for me would be less than 100.
The modern missionary movement? For one thing, that depends upon the mission board. There have been many compromises along the way with the history of modern missions as well as the church at large, so I can't answer concerning a particular mission board unless I knew their view on several areas of doctrine along with their biography.
Generally speaking, Yes, I personally believe it is wrong NOT to support missions. While I know that most Primitive Baptists believe the Great Commission was given only to the Apostles in Matthew 28 but so was the authority to baptize, yet PB's baptize for membership. Myself, I believe the Great Commission extends to the present day.
As far as I know there are some PB's who support missions but they don't call it a mission or missions as such. They are willing to send "helpers" or "workers" to another local church or area to "help" with the work.
Sunday School? I don't find anything for or against it in the Scriptures.
I do find that we should desire the word both milk and meat to grow in knowledge and discernment without restriction as to the confines of the local church or one's age (the only necessity is the ability to read and/or understand it if spoken).
I hope I answered your questions to your satisfaction brother.
BTW, I have nothing against the Primitive Baptists and in fact I admire them because for the most part they are the "salt of the earth". They do seem to have a quarrelsome past but I believe all Baptists have that in common.
HankD