✔ 最佳答案
Surface meaning (字面解):
Just About: 差不多
as far as: 去到盡
The meaning of "just about" here is not really as it means on the surface. It is a polite way of saying "completely".
Therefore, "Just about" here really means: 完全
Going back to your example 1:
"That's just about as far as we go from here":
It means we have totally exhausted all means and can not proceed any further.
我地己經完全去到盡, 冇得再去啦。
For your example 2:
"I have gone just about as far as I can go with this body":
It means I have endured the present state of this body to the limit, and can not endure it anymore.
我對呢個身體依家嘅狀況己經完全忍到盡, 冇得再忍啦。