Hello again!
To test: When you pull on the bottom of the loop after suspending the rope from your fixture point, does it tighten (it should)? Can it be undone/loosened from pulling on the bottom of the loop (It shouldn't)? That's really the only part that matters. I usually do 3-4 loops around my slipknot as it seems more secure (see
https://encrypted-tbn0.gstatic.com/...gC1OgOWjRcqzLfblHweF9vlzFK3xUsKQeaCoGp_Pn9xkM), looks like you only do one ?
If I were you I'd use a rope that's less likely to compress which makes the slip knot more slippy. You don't want the knot to just tighten into itself instead of sliding down. But you'll be able to tell by doing the tests above.
Also 65kg might not account for the extra tensile force suspension will generate. Unless you're absolutely sure a good part of your body weight will be on the ground/otherwise supported, I'd get something a bit stronger.