In a 16-team dynasty IDP league, non-PPR, salary cap league, I have been offered the following:

Jerry Porter for Adalius Thomas

The scoring in our league is as follows:

Offensive Players-start 1 QB, 1-2 RB, 3-4 WR/TE
· Passing/Rushing/Receiving Touchdown 6 points
· Kick Return/Punt Return Touchdown 6 points
· Recover a Fumble for a Touchdown 6 points
· Passing/Rushing/Receiving 2-point Conversion 2 points
· Every 25 Passing Yards 1 point
· Every 10 Rushing Yards 1 point
· Every 10 Receiving Yards 1 point
· Interception -2 points
· Fumble lost -2 points
Defensive Players-start 2-3 DL, 3-4 LB, 3-4 DB
· Touchdowns (including Special Team TDs) 6 points
· Sack 3 points
· Tackle Assist 1 point
· Tackle 1 point
· Interceptions 3 points
· Pass Defense 1 point
· Forced Fumble 3 points
· Fumble Recoveries 3 points
· Safety 2 points

My roster is:
QB: Schaub, Kitna, Stanton, Rosenfels
RB: FWP, MB3, Fargas, Duckett, FJax, Morency
WR/TE: CJ, Plax, Roddy, Hackett, Porter, DWill, Glenn, O. Daniels
DL: Roth, M. Anderson, IAF, J. Moss
LB: Poz, D. Harris, Keiaho, Durant, T. Davis
DB: Pollard, Weddle, Piscitelli, D. Bullocks

Should I sell Porter while his value is highest and get a stud LB in return? Or keep Porter to see if he can reach his potential with a new team? I would most likely not start Porter most weeks (choose between Roddy, Hackett, Porter based on matchups), but would use Adalius in my lineup. Thoughts?

Pretty even offer, but I think I would keep Porter.
U should be able to do better then Thomas, and I usually dont trade offense for defense.

I don't have any problem selling Porter, but I wouldn't call Thomas a stud LB. He'll very likely play OLB this year, which will increase his sack numbers, but won't do his tackle stats any favors. In your scoring system, Thomas is likely to be your LB4, but may not be better than what you can grab off the wire if Durant doesn't start.

I'd pass, you can do better.

An update to this deal. I had rejected the previous deal of Jerry Porter for Adalius Thomas straight up. Now the same owner has proposed another offer of Adalius Thomas and 2010 3rd round pick for Jerry Porter.

Does this tilt the deal in favor of accepting it?

A 3rd round pick three drafts from now has no value for me, even if you're in an all-out rebuilding effort.