My Child's fear for strangers

This sounds exactly like how my oldest daughter was. I enrolled her in a dance class at age 2, where the parents participate. It took 4 months to see progress. The we moved to the next level. Little kids without parents, but kept the same teacher. 1 year of resistance. Lots of positive feedback for good moments, and tons of patience, my daughter was ready for school at 3 1/2. She loved dancing before classes so that's why we chose it, and she still loves it several years later.

Also, you aren't a bad parent if your child cries! At some point during the same struggle you are having, I decided I would not pick her up. I felt like that might be reaffirming her fear that there was something to worry about. She threw the most epic tantrums for about a month. Then she started hanging on to my legs. Then graduated to my hand.

My oldest can still throw the worst fits anyone has ever seen, and she can go on for hours. Our rule is, "throwing a fit wont get you what you want". If i prepare her for a change a long time in advance i find she throws less fits. For example "mommy's going to let you play all by yourself at day care, then I will come back and we can play together." Also as my kid got bigger and started school, i do not teach stranger danger. I simply teach them that we dont go anywhere with a stranger or give them personal information. I dont want my kids to fear people!

Maybe none of what worked for me will work for you, or maybe it will. But good luck on whatever you try. I certainly know how exhausting it can be.

I think you will have to be a little firm and not give in to picking up.  Reassure him but let him know you are not picking him up at every given point.  Introduce others and try to persevere in getting them involved.  Also you could speak to your health visitor who could offer some tips.