I cannot answer all your questions, but there are a few I can answer from 1st hand experience:
The Sendelingsdrift chalets are more or less in a straight row all along the river bank. Haven't been to them all but if one has a better view than another it will be marginal - the riverside is steep and overgrown so not a wonderful view but you are quite close to the water. The chalets kitchens are very well stocked - you shouldn't need anything drastically.
Apparently the situation will change soon but the shop at Sendelingsdrift camp is very badly stocked. Don't rely on anything from there, including fuel from the garage. No unleaded fuel is stocked at any time.
Tatasberg camp has a lovely view on the river, but some distance from the shoreline.
Don't know about Gannakouriep camp.
There are only two ways to enter the Park on the SA side. Most commonly from the southern gate. Can be reached via either Kubus/Eksteenfontein/Lekkersing/Alexander Bay. All depends what type of approach you want - ranging from serious 4x4 to tar/dirt roads. Then there is the pontoon from the Namibian side. You can get there via the N7 - through the Vioolsdrift/Noordoewer border post. Either way you need to sign in at Sendelingsdrift before entering the Park proper. If you have a look at http://www.sanparks.org/forums/viewtopic.php?f=38&t=30206
, you will see there are a few trip reports with a lot of information, listed under the Ai-Ais / Richtersveld heading, including one of my own with some photos. Calculating travelling times based only on distances is difficult. It all depends on the status of the "roads" in the ravines. At this point in time, the roads are mostly badly corrugated. The Park needs some serious rain to get rid of the corrugations, to reinstate the Park as a 4x4 destination.
I found this map I posted some time ago. The sections in red are deep sand and should be negotiated with great care. Enjoy!