Hi David,
>>>>>when you clicked on a certain portion of the attribute, that value would come up and you would be able
>>>>>to change it without having to use your mouse to select the value you wanted to change
Yes, there is a kind of bug (defect) in AutoCAD for Mac that prevent from set focus in Enhanced Attribute Editor to the attribute name you double-clicked to start editing attributes.
But, if you pick on "select block" button in Enhanced Attribute Editor window and then pick on particular attribute in the block - this attribute will be selected and ready for editing in Enhanced Attribute Editor window which will appear just after you select block attribute.

>>>>>tab no longer allows me to go from one value to the next
If you are about Enhanced Attribute Editor, then TAB key doesn't move from one attribute to another in PC version too. On Mac you can use UP and DOWN arrows to move through attributes, then TAB to move focus to attribute value editing field.
NOTE: if you will select "Text boxes and lists" option for "Full keyboard access" in Shortcuts tab of Keyboard pane of macOS System Preferences, you will be able to move between attributes in list with UP & DOWN keys, use TAB to set focus to editing field and return back to attribute list:

I'd suggest you to play with these two settings for "Full keyboard access" and select which one will suit your needs.
If you are about "simple" attribute editing window - ATTEDIT command - than TAB moves focus between attributes on Mac the same way as on PC.