SQL Server For Data Processing

I'm working on a system right now where I have a database (two,
actually, but one is discarded halfway through), but it's created
and used as part of a process (reporting), rather than as the
actual production data repository. I may be keeping the database
permanantly, but it would be completely read-only; once the
process is complete, the database will not change again. This has
me wanting to do a few things that are rather foreign to my usual
experience, and I don't know how many of them are supported.

In several cases, I'm summarizing one table into another by several
fields, and then updating the original table with an ID for the
summary row each source row was summarized into (e.g., I summarize
PlaceAndProductSummary into PlaceSummary, and then populate
PlaceSummaryID in PlaceAndProductSummary). The update of the
source table is much faster if the summary table has a clustered
index on the summarized fields, but all later access will be faster
if the clustered index is on the identity column. I've been
including an ORDER BY the summarized fields in the original insert,
so the identity column is in the same order as the summarized fields,
but I don't know of any way to take advantage of that in the
indexing declarations.

As another approach to the above situation, if I change the
clustered index on a table, and the rows happen to be in the
same order by both indexes, will the table still get rebuilt?

I will never do a roll-back in the process; if an action fails, I
want to raise an error and halt (and I haven't lost any data).
Is there any way to completely turn off logging?

Will I gain anything by marking the database as single-user?

Any indexes that I am not using while I populate the tables, I'm
adding at the end with FillFactor 100, to keep any slack out.
Is there a way to remove all the slack from everything else, at
the end of the process? During a backup operation would be fine.

Thanks,
Bill