Hi GaryNZC
Sounds like your fitness is good an 100km distance and FTP of 216 is pretty good!
The slow heart rate recovery may be a sign of overreaching. Revcovery is slower as one ages (I’m 60, so I know this from experience). You may need to modify your training cycles from 7 days to 10 for example to recover fully).
As others have said changes in RHR aren’t uncommon for a period after pushing yourself.
Wrist based technologies for measuring heart rate have come a long way. They are based on photoplethysmography (shining a light). However, they less accurate than a chest strap for a number of reasons - which is why they aren’t used in sports science or medical research work.
As for the oximeter aspect. Most of the wrist based oximeters aren’t considered accurate enough for scientific work.
An increased respiratory rate (RR) is not uncommon during certain phases of the sleep pattern (during rapid eye movement - REM - sleep). During REM sleep it may double. It should decrease during non-REM sleep. How are you measuring RR? This is another parameter that is difficult to measure accurately - even researchers struggle. Certainly a wrist based technology isn’t going to be accurate here.
If your saturations REALLY drop to below 90% at night (with an accurate meauring technique NOT wrist based) then that may be a concern (do you snore?). Fit people (at sea level) should have a saturation above 95% at rest.
Does this happen at any other time than following your bouts of exercise? If you are concerned it would be worthwhile speaking to your family doctor.