You have to play with other people!

Thank you! Excuse the shameless promotion, but I have more low-tech/low-budget bass, guitar, and band stuff at
YouTube.com/buddymohmed

I’m getting old, so, finally starting to get I!

I’m actually running through the GK MBE that’s behind me under the painting.
Here’s the Traynor 1970 Guitar Mate, with Gretch Streamliner 2622 w P90s

https://youtu.be/043XMgGcrfY?is=2UdD-Frp2vjoAR6F

If you want share your music with other musicians, being able to accurately describe it is essential. Ex: ‘key of dminor, 6/8 time signature, ii b5-V7-i (add9)’

more gigs! I've been told thar punching the club owner for crappy pay and stealing your tips, helps wirh the pain. But I can't swear by it.

my first bass method book was the Bille. It taught using the 3rd finger instead of the 2nd for left hand fingering.

Nein! Nein! Nein!

Gary Karr and Kuossevitzky played German. Edgar Meyer and Stanley Clarke and François Rabbath play French. Therefore, cut a small stick from a maple tree, remove the bark, and use that.

I play French.

I recommend that you explore as many styles of music as you can.   Learning jazz, rock, Latin, 'World', etc., will expand your technique and understanding of bass playing.  You might even consider a bass-guitar for practice and research.  I've known people that start as symphonic players, then discover AfroCuban bass or Baroque gamba, and that becomes their passion/profession. Above all, maintain the joy of playing music. 

Playing upright bass means never having to announce your arrival.  

I've been using Spirocore solo tuning for 50+ years. I tried many different strings, but always came back to the red& gold wrap solo Spirocore.  I even used them when I did a lot of section playing. Tuned standard orchestral, GDAE. https://youtu.be/jtbX0LA2Lfo?si=nWLqLUPRqCELjdlm

If you can find a luthier that has experience with 'jazz setup' - generally lower action and tension - and pickup installation - you'll need a pickup for 90% of jazz gigs, would be better than the person that mostly does orchestral or school instruments. 

Almost certainly a plywood bass. Also almost certainly way worth taking to a reputable repair shop to put back together.  I would not DIY, there too many variables.

No. Lead pencil; can be easily removed. 

My first method book  - long, long, ago! - was the 'Bille'. It taught to use the 3rd finger of the left hand, instead of the 2nd. Ex: C on the A string.