How can I reduce file size using ffv1.3 with ffmpeg?

I have a test file (10 minutes, 449 Mb, mpg2).

If I try to archive it with ffmpeg and ffv1.3 the output file is 2,14 Gb.

ffmpeg -i filepath -acodec copy -vcodec ffv1 -level 3 -coder 1 -context 1 -g 1 outputfilepath

I need losless quality for archival, is there an option to set the video bitrate of ffv1.3?

(in ffmpeg during the conversion I see that it is nearly 20000 kbit/s)

Or is there a conflict between losless and reducing video bitrate?

Using x265 had no effect, it was too big too…

Thanks a lot for your help!