Advice on my next grow.

I'm making plans for my next grow and would like some advice or a critique.

I have a 4x4x7 tent with 400 watts between a cob and quantum board led. I'll be growing in an organic living soil that I will making from 1 part each of worm castings, perlite, and coco. I'm also going to sprout in the final pot hoping for seed to harvest without any transplanting.

I'll be amending the soil with Dr. earths 444, kelp meal, azomite, and mycorrhizae, in addition to nematodes to deal fungus gnats that I expect to run into since I did with my last grow.

I also have on hand high nitrogen bat guano, high phosphorus seabird guano, langbeinite, Dr earths 394 bloom, liquid seaweed , unsulphered black strap molasses, and urb. The urb is a microbial inoculant to kick start the bacteria.

I'll be watering with de-chlorinated tap water ph'd to 6.8. Supplemented with liquid seaweed each watering and making a tea with the urb, molasses and some of the other fertilizers once a week.

I'd like to use just 1 smart pot, I know I won't be able to fill out the whole 4x4 with just 400 watts but I'll be training for a 3x3 canopy using a trellis net. I'd also like to get into a couple weeks of flowering before needing to amend via top dressing with the bloom ferts. I'm expecting between 6 to 8 weeks of vegging with a 8 to 9 week flowering strain.
I'm using 1 pot because of where the tent is, I only have access to one side and it's a pain to reach through the closer pots to water and train the pots that would be behind the closer pots. I know it will take longer than if I did 4 smaller pots.

Assuming all goes according to the timing, will a 7 gallon smart pot be sufficient? Would using a 10 gallon smart pot be better for the longer veg time?

Also is there any other advice anyone can give me with how I will be going about with the setup and soil? Any other amendments you can recomend also.

Thank you.

I think you are better off transplanting once or twice as opposed to trying to stay in one container the entire grow. It helps develop the roots which progressively need more room. It also eliminates the need for heavy feeding with soluble npk later on when the roots finally reach the edge of the pot. Adding fresh compost and soil under the roots regularly also keeps them growing out quickly. Bigger containers are almost always better at regulating moisture if you have the space but ten gal pots in a 16' sq ft space may be overkill. You may need to veg longer than 8 weeks to fill out a trellis. Plus transplants give you the opportunity to sprinkle granular mycorrhizae into the hole in contact with the root ball at each transplant. Don't try to amendthe soil with it globally that is not how it works. Needs to touch the roots.
Use the guanos sparingly. They are highly concentrated but great to add to a tea; loaded with bacteria. Worm compost is more essential than npk inputs. You can never add too much. Diatomaceous earth will kill fungus gnats effectively without the need for nematodes which btw you can acquire naturally for free just by starting a worm bin. Having a worm bin is the best move an organic grower can make to up their game to baller status.
Don't ph your water. That will do nothing as the soil itself sets the ph. I would begin with a good organic base soil like Kellogg's or ocean forest and amend with coco, perlite, and ewc to begin with. Save all your other amendments for when you recycle the soil. Use soluble npk inputs like the liquid seaweed and compost teas to maintain the soil through the first run. It takes several recycles before your soil reaches supernatural status. I suggest using organic plant spikes for slow release npk. I use Jobes brand; they feed for 8 weeks. Perfect for a bloom cycle. You don't need a bloom booster either just put what they need in the soil and give clean water most of the time. You also don't have to change what you give them be it veg or bloom phase. Btw how do you plan to dechlorinize your tap water?