According to this, price in Russia should be much MUCH lower than Canada so you should be able to gift it fine. https://steamdb.info/app/12120/
Alternatively you can also just give him the giftcard
SteamGifts don't allow you to alter your giveaways. I've already suggested gifting the winner the gift card and he refused, he wants the game but the tax differences between Canada to Russia must be higher than the limit.
Which is silly why he would refuse in the first place seeing as he could get more out of it. Must be one heck of a strange guy. In either case if you don't get it at all, I suggest making a ticket to Steamgifts support on what to do.
The worst that could happen is that you get a game marked as not received even though it should be completely possible to gift from Canada to Russia. You just lose a giveaway slot that you can easily get back by making more giveaways than needing to go through all this trouble for someone that seems to not be that entirely grateful to you by making you needing to go through all this trouble in the first place.
If you are dead set on still wanting to get GTA: San Andreas though, that MJunior guy offered to be able to do it from his chat above. I can do it too but he offered first.
Sorry but no thanks, there is a innocent giveaway winner waiting for his prize and i was unable to deliver at the deadline i set for the giveaway. Didn't think GTA San Andreas would've been hard to acquire in the trading market of steam
I can do that for ya, got a humble bundle link or key for it, whichever you prefer