Is it true that with 800 amp circuits and smaller, it is legal to bump-up the OCPD to the next larger size? So essentially I could have parallel 500 kcmil equal to 760 amps, and protect it with an 800 amp breaker? Does it matter if it has single conductors or parallel?
You are correct with the 800a breaker.
Just to verify your cable selection though, to select the cable you start out with 125% of the continuous loads plus 100% of the noncontinuous loads. The cable you select must carry that load based upon 75deg rated cable. Then you select the OCPD to protect the cable. If there isn't an OCPD that is equal to the cable ampacity rating, which is common, you are allowed to select the closest size breaker rating available greater than the cable rating.
If what you are intending to do meet with this requirement then you're good to go. Just verify what you are doing.
Remember that the cable is sized to carry the load, the OCPD is sized to protect the wire.protects the cable such as the 760a rated cable that you have..
How you select the single or multiple cables to accomplish this is of no consequence as long as what you select is sized to carry the load and your cable protects the cable that you selected.
