I followed alog21716 and brought H1:LSC-MOD_RF45_AM_RFSET down to 22.2 and checked that H1:ASC-ODC_AS_A_DC_LT_TH was set to -11000. This dropped the noise down to a level much closer to what it originally was (at least according to the dtt H1_45MHz_Demod_FOM.xml). I tried tweaking the RFSET slightly to see it I could improve it further but it is too hard to tell if it gets better or worse.

Range is back up to ~70Mpc. Screenshot attached of dtt session.