All previous 'fixes' via DOS (BOOTREC /FIXMBR, BOOTREC /FIXBOOT,BOOTREC /REBUILDBCD, etc.) didn't work. Maybe because I'm not comfortable working within DOS and did something wrong.
These are not magic fixes, each one does a specific thing and you shouldn't run fixes just randomly...
Win7 errors are: Boot Manager failed to find OS Loader. Boot configuration data store repair failed. Boot Manager generic failure. I do see the file H:\Windows\Boot\DVD\PCAT\BCD and H:\Windows\Boot\PCAT\bootmgr but 'Access is Denied' for editing. Is access to these folders the problem?
You seem to have pasted some random errors together, can you tell us when each of them happens?
Have you researched these errors? Which suggested fixes did you try and why didn't they work?
Boot Manager failed to find OS Loader.
This means that the Boot Manager either misses configuration to find the OS Loader or it is missing.
Boot configuration data store repair failed.
This means that an attempt to repair the BCD store has failed, it might be corrupt or inaccesible.
Boot Manager generic failure.
This really depends on what you have been doing, doesn't say much...
I do see files [cut] but get 'Access is Denied' for editing.
Just finding the files on the disk and checking their permissions does not makes sense. Note that Windows actually protects you from tempering with it, they are not meant to be edited. If any, the paths you mentioned are kind of irrelevant;
DVD\PCAT means you are looking into the Product Catalog part of the Boot Manager of Installer copied of the DVD.
You could attempt to copy
BCD from that to see whether that has any effect to restore your BCD to an original state, which could work; but don't forget to make a back-up first...
You can gain permission using these instructions, make sure that while doing so that you don't remove any permissions. Also make sure to take a back-up of the old BCD folder in case it doesn't work.