Old Header and Joist in dire need of repair

This message has been edited. Last edited by: K Richner,

I found the 10"x6" header over my garage door has rot in the center of it over the garage door, I want to sister 7 2x12's under it and also sister 3 2x10's to it to go under the floor joists in the garage that is below my kitchen and dining room! I then want to support the new header with 2 2x12's under the new 2x12 header and use 2 2x10's under the 2x10 portion of the header. is it possible to get 16"-17" lag bolts to secure the new header together? I will be cutting drilling and pre-fitting each board for 1/2" lag bolts and gluing each board after cutting them to fit, also what diameter lag should I use 1/2? and how many? to make this work? I would just replace the header but it is one solid beam running the width of my home about 35' and this would be a major project that I cannot afford, so my plan it to over build and auxiliary header to take the load! as far as code this is unlikely going to be a issue were I live the town really does not care I just want to make sure the house is safe anyone have any ideas for this project? I can attach photos of the area in need of help if needed.
Thank You
Ken