Messages

[PST Split software]

First,  do try manual technique:
Just right-click any folder in one PST and then select "Move folder" to move it to another  PST.  If you wish to do this by date, use the unique  Export feature of Outlook, and click the Filter button to select the date range.  Once you have added the items to the new PST, delete them from the old PST location, because they are copied, but it still works fine.
Or else you can use the third party splitter  Like PST Split software, Being a professional software, it provides unlimited features which not only split your large PST Files but do provide different option to split PST Files. 

[Outlook PST repair software]

There are several third party Outlook PST repair software available on the Web that can easily repair badly damaged Outlook PST files without any hassle. This software also allows you to recover deleted or permanently deleted emails and other data from corrupted PST files without losing any original data. The software permits you to access the PST files in DBX, MBOX, MSG, EML, TXT, RTF, HTML, and HTML formats. It is compatible with all versions of MS Outlook including MS Outlook 2016, 2013, 2010, 2007, 2003, 2002, 2000, 98 and 97. 

[Lotus Notes to Outlook]

To convert  NSF to PST format, you can try some easy manual trick instead of using a paid tool. But if in the case the manual trick fails, then you can try a professional Lotus Notes Converter tool. But before that, you must try to transfer the NSF to PST Manually.
So if you cant does it manfully then You can try a  third party tool for converting NSF files to PST format. There are many software companies in the market which provide such utilities. You can try few them. Most of them are available with free version, you can download them and check the software minutely before purchasing the licensed version. 
If you have no idea which one to opt for then you can try free Lotus Notes to Outlook converter of SysInfo. For me, this tool is one of the best tools for the Lotus Notes to Outlook Conversion.