Hi Gary, That is a lot of questions. I can answer some, and point you in the right direction to get the answers to the rest.
First, I have never grown any from seed. If you follow the link I've given, you will find all kinds of discussions on germinating and germinating mixes, etc.
Basically, only the ornamental varieties (basjoo is one) have seeds. All (ornamental and edible) can be propagated by other methods. Replanting pups is one method. Pups are shoots that pop up around the mother plant. They are like suckers, on trees. Bananas are not trees; they are acually a giant herb. What appears to be the trunk, is the pseudo-stem, or false stem. The true stem is underground. Much more on all this at the link.
Another common method of propagation is tissue culture, or cloning. This can be used for seeded and seedless varieties.

Here is a link that might be useful: more answers

What John said. :)

A pseudostem (pstem) is the thing that looks like a stem, but isn't. It is the elongated leaf "stalks" all wrapped around each other. When the plant finally fruits, it pushes up its meristem or growing point which has (before it comes up) already decided to become the flower and it can't revert. That growing point is done and that "tree" will grow no more. Hopefully some tissue on the corm (a bulb-like shortened underground stem) will develop a new growing point. When this comes up it is called a pup.

When young, musas are very tender. But once the woody corm forms they are tough. You can cut off, freeze off, or kill off the leaves and if that pstem doesn't grow back, there are plenty more that will.

The collection of old and young pstems and their shared roots is called a mat.

Musa seeds seem to be fussy about conditions, and difficult to germinate in general, and one person will have great luck with one variety and another person will have great luck with another variety. I've never gotten Sikks to germinate.

Are you doing it from seed as a challenge? Most varieties are available as living plants for varying costs from a number of sources. Commercial growers charge the most. Since most kinds pup quite well and are fairly tough in frost free climates many home growers in Z9 and south sell excess plants for cheap or trade or even give away. Ask around.

If you are able to find homes for a large number of plants, there are tissue culture facilities who sell dozens, if not hundreds, of varieties for under $1.00 each plant (what many people will pay for seeds that never germinate) for a tray of 72 baby plants.

Musa species mixed means mixed seeds, no guarantee of variety.

If you do get germination, keep them very humid until they are a couple inches tall. Keep the grow light just above them. The Miracle Grow soil should be OK. You might do well to add a bit of a fine grade of perlite to keep it light. If you mix your own soil, be sure to use lots of perlite or vermiculite (or a mix). Musa of all sizes, but especially little ones, grow roots far better in light soil and don't like wet mucky soil.

Absolutely you must go slow in adapting them to the outdoors. Outdoors, in the shade, the light intensity is 1000x as great as indoors.

I also bought musa enste seeds from thompson and morgan only one germinated and now it's 3 1/2 feet tall, I always repot in tropical soil and fertilize with 20-20-20 it says on the pack of seeds it's supposed to bloom at 5ft hopefuly. As for overwintering for me it's pretty easy just cut back on watering, and I never give fertilizer in winter.

I expect that you can buy banana plants at any nursery in the SF Bay Area.

A good source for musa seed and rhizomes has been banned from mention in this forum, allegedly because of spam. In pig latin its web site would be called www.annabay-eetray.com. This company has been in business for maybe 40 years and I have always been satisfied with it.

As I recall, musa velutina seed germinates rapidly, but it has been decades since I last grew it.