i'm probably way too slow to you to be helpful, but…
your heart pieces. based on your map (great work, by the way):
1 - hyrule ranch. "master" the middle course. (you have to have completed "impa's gift," but i'm sure you have by now.
2 - the "wild sandstorms" side quest will land you one. you get the quest from the soldiers to the west of the throne room in gerudoville. you beat two lanmola's, and then when you beat the third in northeast-ish gerudo desert, it's a miniboss reward.
3 - when you get thrown in deku jail as part of the plot-march towards the faron rift. it's in a side room.
like i said, you've probably already found these.
AND… what's weird is when i first found this thread, it looked like no one had replied. and now as i scroll up to double-check my work, i can see it's a healthy thread (but i typed all this out before seeing and thus reading all of those). so, sorry, if i'm doubling-up.
(i was thinking, "man, no one helped him? i gotta toss him a bone.")
your three echoes:
• lynel is in eternal forest. you have to look for his hoofprints. (i think someone in or near the forest (maybe it was a sign) says this.)
• moa - this is the ghost from zelda iI: the adventure of link. it's hard to describe the location, but it's basically at the top of the ice/waterfall in hebra (but way up). it won't look like it in game, you'll have to reference the map. go a little bit west of this.
• platboom - stilled desert temple or gerudoville (the small cave on the backside cliff).