1. It is not currently possible to adjust the column widths using the summarize option, though this might make for a nice addition. The DataSummary command uses a similar technique to DocumentTools:-Tabulate, however it doesn't dispatch to that command.
In theory, you can pretty easily recreate a summary table using the Tabulate command. For example:
results := evalf~(Statistics:-DataSummary(Matrix([[3,1130,114694],[4,1527,127368],[3,907,88464],[2,878,96484],[4,995,128007]]))):
DocumentTools:-Tabulate( <map(lhs,results) | map(rhs,results) | map(rhs,results) | map(rhs,results)>, weights = [20,25,25,25]):
2. For saving a table to an image, the only thing I can think of is to grab it using a screenshot (see above).
I'll add an internal ticket for the enhancements discussed above.