Regarding varnish, 5 coats is just a suggestion based on someone's experience. Over bare wood (interior) I do 1 coat of non-blushing epoxy and 4 coats of varnish. But as they say YMMV.
You may want to let your new piece of teak weather a bit rather than trying stains. Alternaitvely you could oil the whole thing which should even up the color.
Silicone caulks just generally don't work well on boats, especially for bedding hardware. Polysulfide caulks work better or in certain cases butyl tape. Since bedding hardware is a PITA, it's better to use the right material.
"Never attribute to malice that which can be adequately explained by stupidity." - Robert A.Heinlein