It's all in the fine tuning with this plant. Don't beat yourself up over it, potential height is a function of nutrient load and light height. You are seeing the results of not having the nutrient load correct, but lights to close can shorten a plant and too far away can create stretch. Again, a balancing act. I am also sure that by finish your buds will be just fine.
I do not use teas or other ammendments at the moment. I will probably start trying teas eventually, but I want to be completely comfortable with my current methods before expanding out. My soil is a mix of an organic bag dirt, coco choir, and perlite. The dirt itself has guano added.
As far as trimming or altering an auto. I trim leaves when tucking just wont work, or when discoloration shows up. I also remove some stuff at the bottom to facilitate watering and airflow. I do not typically train my plants so very little LST experince, I have topped an auto however, with good results. it seems to be a strain sensitive issue. I topped a Dinafem OG Kush auto and it took off. Bot that plant was a larger plant already, I wouldn't try it on ET Dragons or Girl Scout Cookies. Afghan kush Rider might be a good candidate, but It would have to be the taller stretched pheno, not the short bushy one.
The big thing to remember for your next grow is planning. If you clearly define your goals before a seed is dropped and have everything in hand and ready to go with a plan, the whole process gets easier.