Mailing newsletters

I'm planning on mailing a weekly mailing to three separate member groups of about 15,000 subscribers each. I'm using an SMTP server for this.

First, Tribulant Newsletter completely lost its mind on a list this large. Can e-Newsletter handle it or do you try to bring the entire list into memory at once (a bad idea, if you do)?

Second, when mailing, it looks like you've got to leave the browser on the page with the percent done indicator. Is that true? Or can you initiate a mailing and then leave that page? Can you come back to that page to see mailing status?

Can mailings be triggered without the Web interface, like from a cron or a shell script?

Thanks!