Can I list all of my self-employment expenses under "Miscellaneous" Category rather than in specific category like "Advertising, Supplies" etc.? Ends up same amount.

I wouldn't recommend that.  The categories are there for a reason and it creates much less confusion and questions by the IRS.  They don't review returns until much later most of the time, usually at least two years after filing unless there is something that really stands out as abnormal.  You would need to be prepared with all detail backup documents and receipts. Always keep everything with your tax return to verify your entries.