Dear valentino, i would suggest to flush the system first with isopropanol, without column, and then with the mobile phases you described. The rheodyne leak could be due to rotor seal problem, which you either fix (difficult for an inexperienced) or change. There is a youtube video for it i believe. This is usually observed under high pressures when the seal is in moderate condition, or even under low pressure when the seal is heavily damaged. The drops out of the waste capillary could be due to loading more volume than the capacity of the loop which is not a problem.

In addition to the above comments, I would put a dilute portion of acid then base (0.025 N) through the disconnected injector in case the obstruction dissolves.  If this doesn't work, it is time to replace the rotor seal (the guts of the injector).

Here is a link to the manual for the Rheodyne 7125 injector valve. For a quick fix I would suggest disconnecting the valve and immersing it in a container of distilled water and placing it into an ultrasonic bath for a few minutes. Flush the valve as per the manual and then try using it again. You might need to rebuild the valve; you can do this using a 7125-999 Rhebuild kit see 2nd link.

http://www.schambeck-sfd.com/de/pdf/operating-instructions-model-7125-manual-sample-injector.pdf

https://www.idex-hs.com/rhebuildr-kit-for-7125.html

Thank you to everybody, I fixed the problem with a injection of dilute acid and the flush.