Joe, with a 4 inch pot, 9 or 10 seeds is probably about right. I never really count the seeds, just kind of estimate and try to make sure they have a little spacing between them. Any more than that, however, you'll find you'll run into watering and feeding problems during the summer.
The size of the pots a seeder uses most often is determined by the seeders themselves. In other words, whatever works out best for them. And in your first few years of seeding, I'm sure you'll change, modify and eventually develop a system that's just right for you and your total surrounding setup and the size pot you use will fall into place along with all that. For instance, my Dad's system was to plant about 50 Asiatic seeds in small 4 or 5 inch pots and then as soon as they had a good full cotyledon, he'd dump them out and replant them, four or five to a 1 gallon pot, which was to become their permanent home until he sold them the following year or two. While, that was different than how I do it, It worked very well for him.
As far as the first feeding goes, I start that as soon as I see the first true leaf and I always feed and water from the bottom up. For the first few feedings (or about 6 weeks) I use a 4-10-3 liquid fertilizer. The directions call out 3 and a half tablespoons per gallon of water, but I cut that back to about half the amount suggested because the plants are so small. The reason for the high phosphate is that it is a good root stimulator and I want to generate lots of roots quickly at the stage--lots of them!. After about 6 weeks and when I have a second leaf growing, I'll start upping the nitrogen numbers with liquid 15-10-10 fortified with trace elements, for all those tons of roots to soak up and that will start putting up lots of green. And the more green you've got the bigger the bulb is growing. By mid summer everything will be happy. The bulbs, the foliage and you--all will be happy. Around Labor Day or shortly after, I stop feeding entirely, depending on residuals to wane down the season along with reduced watering and the natural reduced daylight.
And don't forget--let things get a little on the dry side between your watering and feeding.
