On one of the pictures which shows the BAOR underlined and in heavy print, the column to the right shows "Lt (RARO)" plus a date. That is Lieutenant (going by previous information a 2nd Lt) and RARO stands for Regular Army Reserve of Officers.
DAAG = Deputy Assistant Adjutant General
"SoS BAOR on Class A release" seems to mean that he was struck off strength of the regiment in the BAOR and registered to the Class A release, which was to do with demobilisation and return to civvy street. However, he may have remained on the reservist list and may then have been liable to be called up to the colours again. From what I've gleaned online, a regular soldier would have signed up for "x" years' service and then may have also signed up for the reservists. I *think* the Class A release refers to this, but I haven't been able to tie it down for you completely I'm afraid. Having said that, the fact that his service record shows RARO may well lend a little bit of support to the idea of him being in the Reserves. The dates in the column next to "RARO" may show his release date as 1951: "R/S" may mean "Released from Service"?
I'm sure others more knowledgeable than me will be able to direct you more accurately.
RRTB