HQ
1x Librarian w/ Force Dome, The Avenger, Bolt Pistol, Force Weapon, Jump Pack - 125
excellent choice. The assault squad is NOT supposed to fight against things that are truly scary in hand to hand... they aren't good enough. Seriously, a chappy may give you like 6-7 extra hits when you charge, while a librarian casting avenger can bring down 5-6 (or more) marines in a single casting. melta weaponry (edit- note that the melta must be from a different squad, so you can fire on the disembarked occupants) + avenger is scary as hell, because you can pen6 a rhino, force them to disembark where the rhino used to be (a tight formation) and then lay down the template love on them, wiping out entire marine squads. the librarian + assault squad combo is one I use very often, because its great for delivering 3 template weapons where they are needed. This squad is anti-light to medium infantry... keep it away from heavy infantry like terminators, because even with a chappy, you won't kill them. i'd also drop force dome for null zone. There may come a time when your opponent has some terminators on the table, you have your
tac marines ready to rapid fire plasmas into them, and you need to ensure they go down. Null zone is great for this.
Elites
1x 5 man Sternguard Veteran Squad w/ 2 Missile Launchers - 135
Agreed with above posters. missile launchers in sternguard are a bad idea. If you want a fire support sternguard unit, take lascannons... a 5 man unit with 2 lascannons is 155 points, while a similar
dev squad is 160 points. That said, I don't really think sternguard have a place in 1000 point lists, because they are just too expensive on a per model basis.
Troops
2x 10 man Tac Squads w/ Missile Launcher, Plasma Gun; Sgt. w/ Combi-Plasma - 190 each
should work well enough for you, but I really think you need rhinos for this to work. Without mobility, your plasma guns won't be rapid firing anything important, and won't really do too much. Drop the sternguard, get these guys transports, and consider giving your sarges fists instead of plasmas... at this points level, its important your army is versatile, so you can do multiple things with one squad. Its likely they will end up in hand to hand at some point, so make sure they are ready for it.
Fast Attack
1x 10 man Assault Squad w/ BP and CCW, 1 with Flamer, 1 with Plasma Pistol; Sgt. w/ Bolt Pistol, Powerfist - 240
Should work fine. I'd drop the pistol for a second flamer, and give the sarge a thunderhammer, but thats just me.
Heavy
Vindicator w/ Storm Bolter, Demolisher Cannon, Searchlight, Smoke Launchers - 115
try to find the extra points to buy it a seige shield. Also, unless you get rhinos, don't use this. It would be the only vehicle on the table, and all anti-vehicle weapons would target it, making its use short-lived.