New Door, adjustable sill problem

I just put in a new door for our entryway. The old door was all wood, weighed about 3,000 lbs and was just drafty, it was time for a new one.
So after all was said and done I put the new door in. Everything was level. The bottom of the door was just a little off from touching the sill and I could feel the cold air rushing in. So I decided to use the screws that are on the adjustable sill to raise the sill so it would create the proper seal.
I turned the 4 screws counter-clockwise to raise the sill but the sill didn't budge. The directions said you'd only have to turn these screws a half turn.
The last screw on the right of the door was VERY hard to turn.
Needless to say there is a large enough gap there that the freezing cold air just blows in.
Of course the door was already secured to the opening. so taking the door out is basically out of the question.
Any ideas?
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

i don't know about the adjustable sill so much, but one option is to just replace the weather stripping on the base of the door with something thicker - even if in only one section of the door. is the door square with the top jamb, or does that slope as well?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think they're called "door sweeps" and they go on the bottom edge of the door, and when the door's closed, they're tight against the sill. Hardware store item. Or, try another adjustable sill.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Unless it's a left handed thread I would think turning clockwise would drive the dcrew down and riase the threshhold. No experience per se. Just a guess. You probably tired it both way already though before posting.

Wonder if it got siliconed.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.