I've mulled over this for some time and also consulted with others. You are correct that parts of this must be shown as special material with a blank line before and after, and with the signs of operation and comparison aligned for computation. Remember that the spatial portion of the expression does not require the use of the numeric indicator. The color is usually disregarded. The text shown in italics (to the right of the expressions) are what we call "author comments". They are usually brailled on the same line following the expression to which they refer. Transcribers often enclose these remarks within parentheses. An explanation should be included on the transcriber's note page of how these are handled in braille. I think this is the best solution, however it is not the only one. Some transcriber's take these comments to a new line. Others key them when they will not fit on the line.
I cannot point you to a rule for this type of format, and the opinions vary of how it should be done. Once you have established a format, just be consistent with it!
Hope this helps.