Low throttle hover, MAG issues, and DSHOT600

That link has an access requirement. But to answer your 1st questions ignore the warning in Mission Planner for parameters values out of range. These ranges are not up to date with all parameters. There is nothing unusual about a MOT_THST_HOVER value of .18

Read thru the 7" LR build blog for some helpful tips:
7" LR
Don’t copy the parameter file though it’s on 6S power.