Are there some other surcharges on the 29Euro, or did I misunderstand something?
Regarding trip 2, you mentioned a CNL option was available. However, looking at the booking engine and http://www.bahn.com/i/view/mdb/bahnintern/international/schweden/MDB81178-cnl_all_routes_at_a_glance.pdf the two lines don't appear to connect/have a night option. As it's not so long it doesn't seem so bad, but if there is a night option, I'd like to consider it.
Regarding trip 4, I've found why I'm not finding any sleeping information. I found an evening Artesia running at 8 p.m. from Paris to Milan in November, which would be preferable, but in December, there's only a midday one. It turns out that "Due to works planned on the french railway network, the Artesia night trains between Paris and Venice (trains nr 221 and 220), are temporary unavailable for bookings on the following travel dates:" I'm not sure what that means as it says bookings are "temporarily" unavailable but if they're doing trackwork, I would presume that would mean the services are permanently unavailable on those dates.
I also found that there's a strike of Italian sleeping car workers so they aren't selling any couchettes nor sleeping cars on the Paris-Milan route - nor are there any restaurant facilities at the moment.