1. See other post.
2. Truss rod is adjusted before strings - you want the fretboard to be very slightly convex (curved) once you have the strings on - if you try to adjust the truss rod with the strings on you are likely to damage it as you're working against the neck and the strings.
3. Process is no different for bass than guitar. If you find a video that works for you - go with that one.
4. Will depend on the bass and playing style - I like low and fast, but some like a little higher action because they dig into the strings a little. Some information here: https://support.fender.com/hc/en-us/...itar-properly- and here: https://www.youtube.com/watch?v=c2DlwxSIPA0
5. Take your time - truss rods are strong, but you are putting a lot of pressure on them - give the neck time to adjust. You're close to the end and taking your time now will give the best chance for a good outcome.

PS: Usually there are strings in a kit - not sure why you didn't get some - don't worry you didn't miss out on much - they are not the greatest quality and I haven't used mine for anything apart from setting up guitars. BTW know your pain with how expensive bass strings are - even worse if you look at flatwounds and higher end...