Your amount of addons, both ULX and Non-ULX related, makes troubleshooting any server startup challenging.
Does your server start normally without any addons or workshop subscriptions?
Several troubleshooting recommendations.
First, rule out it's ULib (or ULX) causing the issue - shut server down, remove/unsubscribe the ULib and ULX addon, and restart.
Yes, this will break any staff structure you have that weren't added by you manually to Gmod's default '/settings/users.txt', but at least you/we'll know.
Does server halt on load?
If removing fixes, let's make sure a non-vanilla ULX module isn't causing issue.
Add ULib and ULX back, then try removing ALL non-vanilla 3rd party addons for ULib/ULX.
That is, ONLY try using stuff TeamUlysses has written.
Heck, even if we've written it, just use ULib and ULX.
If removing all the non-TeamUlysses addons fixes, great. You know your issue. Start troubleshooting those.
IF you still have issue when only having ULib and ULX, make sure your autopromote hasn't ruined you.
Many times we've seen lag due to (too large) /data/ulib/users.txt, due mainly to the (imo) poorly conceived and/or configured addon
Mounting Addon '[Offical] Autopromote (APromote) for ULX' (226312488)
I understand wanting to reward players for staying/coming back, but too many times I believe people set these auto promotion limits entirely too low.
Or, without an active good working AFK script, people join your server before going out/to bed for the day and climb into the autopromoted ranks, filling files.
Not knowing your config, you may be subject to that large file.
Add Ulib/ULX back.
Remove, after backing up, your /data/ulib/users.txt
(sounds like you already have backups available elsewhere)
Start server back up - does it halt/freeze?
If not, shutdown server, write back your users.txt file?
Yes? Likely time to clean users/start fresh and remove autopromote.
Let's start with those two big first projects.