Your last baby pic is looking like a mostly indica with it's broad leaves... that's great since you're growing indoors.
1. Yeah... ProMix is a soil product. It has some really good stuff in it although I've never used it. Are you near a store that specializes in indoor gardening/hydroponics? They have more choices that people here are more likely to use such as Foxfarm brand soils Ocean Forest and Happy Frog as well as a nice soiless product called Light Warrior...
2. NO! you don't want to use straight worm castings... use it as an addition to your soil mix.
3. Vermiculite is used the same as perlite... to lighten your soil and improve drainage. I prefer to use chunky perlite which is only found at indoor gardening stores.
4. I like to use a soil mix of about 25% Ocean Forest, 25% Roots brand soil mix, 15% Light Warrior, an additional 20% of chunky perlite added and 15% worm castings. F.Y.I... don't use any water absorbing crystals in your soil mix. Great mj growing requires the soil to dry out between waterings and this slows that process.
Your regular fluoro lights will work fine for vegging although I'd suggest getting another one to add to the setup. As long as you keep your lights an inch or two from the leaves they will do well. A 400w HPS is a great choice for a small personal grow setup. I'm with The Hemp Goddess on the need for an air cooled reflector. I can't stress enough how much the temps need to be kept down in the mid to upper 70's for dank bud. If you get a "cool tube" style of reflector and a good inline fan for pulling the heat off of your light and routing it out of your grow room you'll be much closer to an environment condusive for gooey bud. And if you do... what are you going to do about the smell? You'll need a good carbon filter too if you plan on growing stinky bud... More stuff to spend money on!
As far as nutes go... Since you're in MG soil don't add anything for about a month imho as it's already in the soil. After you have vegged for about 4-6 weeks and the plant is root bound in their current pot you'll transplant to a larger container i.e. 3 gallon, 5 gallon, 7 gallon, etc... depending on what size plants you are growing. I'd suggest transplanting them into one of the quality soils I mentioned above.
Scheduling... the days that the seed bank is mentioning is the amount of days the strain typically takes til harvest. How much you veg depends on many factors such as strain, your veg lights and how much grow space you have vertically. Remember, indicas often double in size when you flower them and sativa varieties can grow to more than 3x their height...
Lots to think about... don't overwhelm yourself. Take your time and be a good student of this amazing plant. Take it one day at a time and if you apply yourself you can master this hobby.
Good Luck and Happy Growing!