What is "Sikus"?
Rashi: It is the name of an idolatry.
Radak: It is like "Haskes u'Shma" (Devarim 27:9) - they hearken to idolatry.
What is "Malkechem"?
Radak: It refers to Kochav; idolatry was made on its name. [The verse] calls it king, for they consider it king over them.
What is the significance of carrying their king Sikus?
Rashi: This returns to the punishments above - "Choshech Yom Hashem v'Lo Ohr" (20). You will carry your idols to Galus with you; the enemies will make you carry them on your necks.
Radak: You did not accept Hashem's Mitzvos, and you accept and bear Avodah of your king Sikus.
Radak citing Targum Yonasan: You will take Sikus, the bread of your priests. Radak - he similarly translated "v'Kilel b'Malko" (Yeshayah 8:21) - he will disgrace the bread of your priests. Some texts of Yonasan there say Pesachreichon (your idolatry). He similarly translated "veha'Nishba'im b'Malkam" (Tzefanyah 1:5).
Malbim: This refers to "Choshech Yom Hashem v'Lo Ohr" (20). You will be exiled. Your Korbanos and Chagim will not help you. You will go to Galus with the idols that you made. They made Sukos for the Avodah of Molech - "v'Anshei Bavel Asu Es Sukos Bnos" (Melachim II, 17:30). Also, when they left Egypt they camped in Sukos, and carried their dough before it fermented. Our verse adopts a metaphor that when they left Yerushalayim, they carried Sukos ha'Molech and the dough for the food of the idol.
What is "Kiyun"?
Rashi: It is the name of an idolatry.
Radak #1, Malbim: This is like "veha'Nashim Lashos Batzek La'asos Kavanim" (Yirmeyah 7:18). These are kinds of food made from dough, for idolatry (refer to Yirmeyah 7:18:2:2).
Radak #2: It is the 'star' Shabtai (Saturn) in the Heavenly legion. It is called similarly in Arabic and Persian.
Why does it say "Kochav Eloheichem Asher Asisem Lachem"?
Radak: Kochav is a big star in the Heavenly legion. It is like a king over its legion. They attributed divinity to it. The same applies to "Lekater li'Mleches ha'Shamayim", like I explained in Yirmeyah (refer to Yirmeyah 44:17:1:1-2). They made an image, and made it god over them.