No sill slope, Red Iron house

I have a <20 year old house. It's a red iron build with finished interior. My windows (on the outside) have about an 8 inch sill, and unfortunately a few of them don't appear to have any slope. This has lead to some water intrusion on a couple of windows.

outside view after scraping sealant

I was originally going to just re-caulk them and see how well that does, but it doesn't seem like a good long term solution. I would like to get them sloped away.

The difficult part is the underneath the sill is a 2x8, and the window rests on a separate (x2) 2x4's.

Inside view, looking up, black arrow is the sheet metal sill running under window

Above the red iron on the red arrow is the 2x6.

I was thinking to remove the 2x6 and give it a slope, but I assume it runs horizontally quite a distance and would require me to remove way more material than I'd like.

I was also considering slamming some shims under the window and hopefully raising the inside up enough to give it a slope, but it doesn't seem to have the upward clearance.

I already have to remove quite a bit of the interior drywall and probably a decent amount of the wood to fix the damage, so pretty much any fix is doable.

also this is only window 1 of probably 3 that are going to need a similar fix.

Thank you!