Your plan sounds like it should work out ok. The base price for multiline UDP is $100 plus $20 per line. Discounts don't apply unless you're military or a veteran. In the marketing material they're breaking it down to $45 per line with 4 lines. For 5 lines that's $40 per line which seems like a pretty damn good deal.
The CS is mediocre, like the other 3 carriers. None of the carriers have good CS really, they all seem to be about the same anymore.