If the processor manufacturer is honest and you follow their guidelines there should be no impact to reliability. You can often do bizarre and wonderful things that a manufacturer won't even want to _see_, but that work fine in practice -- so if you're going off the data sheet you should be OK.
You'd have to check. You'll be pulling it high with a resistor which will flow some current into the 3.3V supply -- it's up to you to make sure the voltage gets high enough. I wouldn't do this unless I had to
-- I'd use HCT or ACT parts if I could.
See above comment. You can trade off speed, fanout and power consumption by adjusting your pull-up resistor.
Read all data sheets carefully, and think hard. In general a TTL compatible 5V CMOS part should be fine with 3.3V logic.
If you pull up to 5V this _should_ work, assuming that the 3.3V part allows it and doesn't smoke.
Two final suggestions:
One: See if you can get app engineering support from the processor vendor or from the distributor. I've always gotten good support and I've never been involved in any high-volume stuff. There should be an app engineer out there who's job it is to make you happy with that processor, if there isn't you should be questioning your choice of manufacturer and/or distributor.
Two: Allow me to repeat my advise about reading all data sheets carefully and thinking hard. All the information should be there if you dig for it or if your local applications engineer points it out. Having said that, you're the one who's ultimately responsible for making it work so you shouldn't feel like you're doing it b'guess and b'gosh.