How to deal with anxiety caused by dangerous riding conditions stemming from poor lane design and inconsiderate fellow road users?
1 Avoid obstacles
There's not too much you can do about this. That school almost next to your home means you'll always be stuck in student-rush hour no matter what you do. Except maybe if you can go around the school area in a relatively small detour. Cycling on a quiet parallel road may be well worth the extra few 100 meters.
2 Be noticeable
Wear high visibility clothing (fluo vests, reflectors, clear lights when it's dark). Especially useful when the other cyclist isn't visible. At least they'll clearly SEE YOU and will evade you.
3 Loud bell
Get yourself a nice loud bicycle bell. One that you can hear from a couple houses away. Use that bell any time there's someone blocking your path, and use it early. Don't wait till you're right behind them. If you ring your bell early they should have just enough time to look behind them, see you and move out of the way when you reach them.
This one works really well if there's someone walking their dog. Given enough time they'll move their dog besides them and maybe force it to sit down, or at least in a position where they can safely keep the dog away from traffic. You might still have to slow down a bit to safely pass them.

Someone riding middle of the bike trail? -&gt; ring your bell
2 people riding side by side not leaving room for you to pass? -&gt; ring your bell
pedestrian not really looking taking up too much space? -&gt; ring your bell
someone driving unsafe with cell phone that you can't pass -&gt; ring your bell

Moreover ringing before a turn with no visibility is the only way to make your presence known without a mirror or stopping. (This is actually the main and intended use of car horns in a lot of countries)
Most of the times (sadly not 100%) they'll make room for you to pass safely when they hear a loud bell ringing.
4 Plan for slowdowns
You mentioned autism. A lot of your anxiety might come from not being able to ride at your expected pace to deal with those &quot;unsafe&quot; situations. If you plan on slowing down at least 10 times during your ride, some of those close to a standstill, and leave enough time to arrive at your destination in time it might take most of that anxiety away. (Note: I don't have autism myself and have only a bit of experience with coworkers/family members on the spectrum, not sure if this hint really works for you).
5 Get used to cycling in calm situations first
Instead of forcing yourself on a fixed hour to get to work in time. Try going to a grocery store in the weekend on a bike to get some minor supplies. You can plan this small trip on a slow hour when you know there'll be few obstacles. If you can't get used to the short bike trips that way, you're probably better of using public transport instead.
Final note
Although most people on this stack will likely not agree with this statement I still think it's true for certain people:

There's nothing wrong with not riding a bike.

I have an uncle that never learned to ride a bike. He always got everywhere he needed and is happy that way. If you don't like riding your bike then don't ride your bike. Public transport in Belgium is usually good enough (although not optimal) to commute to work and even do grocery shopping or visit family members.