I don't know yet if its possible to freeze the HP but if you play enough with values in battles you'll notice that hp sometimes glitches, even so, I think that at the end, the battle wont be verified.
Anything else that its not inside a campaign battle must be harder to change, I ve noticed that the campaign battle runs in offline mode, if you turn off your data/wifi, even if you get a pop up that there s no connection, the battle runs in the background. I think that this is something that might be exploitable, we must change something inside a battle then the results are sent to their servers.
About the values,you could try saving them to txt then importing them.