Structures

1. I need use my blocks from mod into that and also vanilla one
1. This is simply Just run Client in MCreator and Build your dungeon on Flat World type than use Minecraft Structure block and save your dungeon than close minecraft and in MCreator in Workspace tab you have small tab called Structures click it and on top you will see button that says "Import Structure from Minecraft" Click it and select your Dungeon

2. Want add treasure chest
2. IDK about this I know that in past it was required some coding to make chests to spawn with loot but try to do it with MC Structure block it should save loot chests too

3. Wanna allow random spawners on exact spots
3. Also simply just copy one structure but every time you save it just change spawners before save, you can also made it with procedures but then it will be just pig spawners :L

4. Wanna have 3 sizes Small Middle and Large that are possible to generate (need 3 elements or 1)
4. Every structure that you made is one separated mod element

5 Wanna made boss rooms that is always last room
5. You can make Procedure for block that will be checking on Every tick update for blocks on specific locations than when this procedure will find Air instead of This block it will have to destroy doors block

6. Wanna allow it just in specific chunk
6. When making new Structure element you are able to set the specific biome for it to spawn

Additional Info:
Made one Big structure instead of small rooms 
and build it in stage patterns like it was in Hack/Mine mod where you had Battle towers that had rise difficulty with every floor

What is the structure block? Where can i find it?

/give PLAYERNAME minecraft:structure_Block