Ah! found what I was looking for... you could also probably find it on the WDFW chum website but here it is in unillustrated form.

chum fry fresh from the river are 30-35mm total length.

they reach fingerling size (~65mm total length) after approximately 30-40 days feeding in nearshore waters.

at this point they migrate to deeper waters.

note: at all life stages above the fish have parr marks.

As for your question about amphipods. The buggers come in a variety of drab colors ranging from pale gray to dull green to crustacean white(like the color of white shrimp, semi-translucent). However, you probably don't want to use the orange scuds that imitate dead ones in lakes. The green versions however should work well. There's much room for experimenting with different colors, not to mention on some beaches they are camo colored.

I don't know much about forage fish(baitfish), but I can say that right now the herring, sand lance, smelt are all spawning. In addition to using minnow type flies I just recently came up with the idea to affix very small beads of glue on a piece of green yarn or green cloth(a nice strip of seaweed green colored shirt if you can find one.

You might want to pose your sand lance question to the guys on the main board like Downriggin since they would be more in tune with size of these fish at various times of the year.