Hi,
I dont have answers for all your queries, but still i want to share a little.
1) OVI Suite is not a replacement for PC suite.
Yes atleast for near future till nokia comes up with all applications bundled under one umbrella (Having all the applications of Nokia PC Suite + Nokia OVI Suite). As of now not all the devices are supported by Nokia OVI Suite except NSeries and some other phones. It has to think of Users who are using Mac too.
2) If storing messages safely on your PC is the main concern means then, you can install Nokia Communication Centre which is part of Nokia PC Suite 7.0.x.x and above, which will store your messages to the PC. You can also use Content copier to backup the messages and install Noki software to view what exactly got stored on backup file(.nbu). It is unwritten law (Correct me if i am wrong), data(image/video/Text message/Multimedia message/Sound files) which is synced with Nokia lifeblog will not sync again with Nokia photos and vice versa

Reason behind this could may be to avoid redundancy (Chances are there files may be duplicated twice which may lead to more memory space on your PC) This is my assumption. To conclude data synced once with Nokia lifeblog cannot be (re)synched again with Nokia Photos and vice versa as well as with same software which you have synced already. One way of doing this for images and videos could be sync images with lifeblog and then mark those as favorites and then sync it again with nokia photos, then it may sync twice.
3) Lifeblog is not shown in Nokia OVI Suite. OVI Suite do have option to import the data from lifeblog, this may be because, nokia lifeblog is going to be replaced by Nokia photos. If you observe earlier Nseries phones will have lifeblog on the phone N73, N76 etc, but Nokia N 78 has got Nokia photos built in along with the device instead of lifeblog(device). Yes i do agree about sms part, as i mentioned earlier, if storing the messages safely on your pc is your main concern means, you can use Nokia communicaton centre.
These are my comments as an user of Nokia pc softwares. Sure your comments will be a constructive feedback for those who are developing nokia softwares.