Once a phone gets old, it tends to operate in sort of binary way: Instead of using intermediate power states it flips between max frequency and load and idle states(300mhz or inactive cores in case of the S5). Which is bad for the batter...
AFAIK the popular Broadcom Wifi/BT combo chips have FM radio support or can emulate one via firmware and GP ports. But some external hardware and wiring should be also necessary and missing on the S5.
For the second issue i would ensure that in developer settings the (re-translated) option "Always allow apps to use external memory" is set.
The first problem reminds me of the timeout issues i frequently had when transferring files via a sync sof...
For stability (and battery) issues i switched from RR to Lineage. Rock stable now, at least. What i didn't test prior to switching to another rom was whether the stability issues came from too much consecutive dirty flashing, so a clean install mi...