Salamu Alykum brother Anwar.
I think I understand what you are saying when you mentioned
" If wine is forbidden outright by saying avoid khamr then what is the point of telling people not to pray when drunk or mentioning a more definitive word for alcoholic drink (sakar) and associating it with goodly provision? "
I think maybe your right, there wouldn't really be a point to say stay away from prayer in verse 4:43 because its obvious its already forbidden, so in other words what you mean is it could be suggesting that just don't be drunk when you approach prayer but drink after or before. I mean I can see the argument there. But now you would have to make sense of all the other verses of the word KHAMR and in my opinion there will always be confusions and debates and to many meanings being twisted.
I think when taking the word KHAMR AND SUKARA to mean the same thing, I would agree with you, but then again it wouldn't make sense to me many other places in the Quran.
I think whats a good idea if we consult the verse 4:43
Yusuf Ali
O ye who believe! Approach not prayers with a mind befogged, until ye can understand all that ye say,- nor in a state of ceremonial impurity (Except when travelling on the road), until after washing your whole body. If ye are ill, or on a journey, or one of you cometh from offices of nature, or ye have been in contact with women, and ye find no water, then take for yourselves clean sand or earth, and rub therewith your faces and hands. For Allah doth blot out sins and forgive again and again.
The arabic word SUKARA in my opinion has very little to do with drinking physically. According to the verse above, the word SUKARA means a person not being his NORMAL SELF. This could be a angry person, a person who's confused, who's lost and has to much stress, thinking about life, business, money, relationships and not focused. And could also include being in a state of drunkenness. But not limited to that. I think what GOD is telling us is when we approach prayer be focused and leave the worldly views behind and understand what we are saying and asking before we start to pray.
Now KHAMR i believe does mean alcohol and intoxicants , or anything that is harmful and can cause damage or conceal the normal human being. Example, alcohol, drugs, intoxicants, natural or unnatural, we are told to stay away.
However from my opinion I try to take the best meaning from the Quran and to be honest with myself, and the Quran is consistent with its self. This is the only way I can see this topic make sense.
I based my opinion after reading brother Josephs article on intoxicants, which I found to be very helpful and well clarified with proof
http://quransmessage.com/pdfs/Intoxication.pdfI hope this helps
Peace