Re: Getting closer...
Use PuTTYgen to convert your key to .ppk format.
https://winscp.net/eng/docs/ui_puttygen#other_formats
WinSCP GUI can do that too:
https://winscp.net/eng/docs/ui_login_authentication#private_key
https://winscp.net/eng/docs/ui_puttygen#other_formats
WinSCP GUI can do that too:
https://winscp.net/eng/docs/ui_login_authentication#private_key