CQPolitics House Ratings 2010

[Kaine for Senate '18]

I don't even think Minnick is a Toss-Up; I think it's a Lean GOP district.

[Kaine for Senate '18]

There are 16 Districts with a CPVI of >R+10 represented by a Democrat:

MS-04 (R+20, Gene Taylor)
TX-17 (R+20, Chet Edwards)
ID-01 (R+18, Walt Minnick)
AL-02 (R+16, Bobby Bright)
UT-02 (R+15, Jim Matheson)
MS-01 (R+14, Travis Childers)
MO-04 (R+14, Ike Skelton)
OK-02 (R+14, Dan Boren)
MD-01 (R+13, Frank Kratovil)
TN-04 (R+13, Lincoln Davis)
TN-06 (R+13, Bart Gordon)
AL-05 (R+12, Parker Griffith)
LA-03 (R+12, Charlie Melancon)
VA-09 (R+11, Rick Boucher)
GA-08 (R+10, Jim Marshall)
ND-AL (R+10, Earl Pomeroy)

Taylor, Edwards, Matheson, Skelton, Boren, Davis, Gordon, Boucher, Marshall, and Pomeroy are probably safe, leaving 6 prime pickups among these seats.

[Kaine for Senate '18]

Others - Melancon is running for higher office, isn't he? Otherwise I'd add it to the list above, as an open race that certainly favors Republicans.

Exactly.  If Melancon decides not to run for the Senate, then his seat will be safe.