I would try to get something in there like the dental tool and loosen it. Maybe brake it up into small pieces shop vac'ing with a crevice nozzle at the same time. If that doesn't do it, at least if you could drill some holes in the foam with a long bit to make channels, that could work as well. I think sill pans are most critical with brick veneer and stucco exteriors, probably not so much with lap sidings. If your windows are flashed properly, you might be okay unless you have brick or stucco, then you definetely need a place for moisture and water to channel out over the sill pan.

Depending on the gap around your windows you may need to use a backer rod (foam rope) before you caulk. Usually if you have a gap over a quarter inch you should apply the backer rod. If you had Pella windows it would be required or void your warranty. You could use the Dynaflex Michael referred to or if that's not available you could use Sikaflex, Novaflex or Quad. We use Quad most the time on exterior applications. You could use clear if you would like to but I'd recommend getting the color to match the exterior of your window, assuming you've got the clad exterior. Since your DH was the GC (General Contractor) I would have hoped he did some research on brick or stucco applications. Hopefully who ever applied the exterior wall covering taped (or flashed) off the windows first. In most states taping off the windows and a drip cap are code. Here in MN they go one step further and require us to pan the bottom sill plate before we install the window. Fortunate for you the Marvin window comes with a drip cap already applied in most cases. My biggest concern would be the individuals hanging the windows not back caulking the nail fins before they were set. This would void your warranty and give you nothing to fall back on if the window itself failed. Hopefully if it fails, it would be sash related and not require complete removal of the window. In that case you'll be safe from them looking behind the nail fin. If your home is completely bricked all the way around any window removal would be a nightmare. If the front is the only bricked portion of the home then you may be able to get your siding off to inspect the windows. I know this is heart breaking but it will save you catastrophic events down the road. Hopefully you'll be able to find the leak and shut it off easily. I would highly recommend using a professional caulker to seal around your windows. It would be well worth the expense. Good Luck!!!

Thank you! The rocker isn't required...I go back and forth on it, honestly, whether to make a spot for it and keep it or not. I love the styling, but it needs recaned. COVID and forced work from home has definitely created some issues (the filing cabinet and desk) in making it even more cluttered. The easel can be folded into a box and stored. It's a long story, but it was a gift from my husband, but unfortunately not highly useful for watercolor painting (what I dabble in), so I started using it for display so at least it was used at all. The ratan drawer set only holds video game components- which based on how frequently they are used, could be stored in a box in the closet under the stairs just fine. Behind the easel are two dvd storage towers. Again, pretty optional and really need pared down to what we actually want to keep. The shelves next to the freezer are the kid's book and maker space shelves right now...but it's ugly as all get out. I need to sit down and think about what they really need for space, and create it instead of just using those two black bookcases because they are there. But all of those books are kid books, as opposed to the wall shelf which is all adult books. The other big bookshelf is only records for the record player, and a few board games (that we never play. Need to declutter those. The played ones are upstairs by the table.) I agree the decor items don't look that good on the bookshelf...but I don't know what to do with them elswhere in our house. There's really no other place for knickknacks, and honestly that's the extent of our non-Christmas knickknacks. Almost all of the pictures and items have a personal history that is strong enough to keep them.

Did they use latex caulk? Part of the problem or all of it may be because they smeared it on which is giving grime a larger area collect on and more grooves to sit in. Typically I use Quad OSI and I lay down a bead without tooling it. I don’t use any caulk where the casing meets the sill and there should only be a small caulk joint where the window meets the sill. They are either incompetent, hiding mistakes or both. The best would be to remove and reapply, but as you were told it isnt easy and the aluminum could get damaged. I’d try some cleaners on it that are safe for paint.