First let me say, "great reading!" You all are certainly reading with your eyes wide open to God's unified work in redemptive history. When the Bible is read this way much of its wonder and majesty is seen properly and then the outcome of seeing it rightly is worship for the "God who was, and is and is to come!" Praise the LORD!

In answer to your question regarding the unity of Daniel and Revelation, "Yes." In short it is argued that Daniel, particularly chapters 2 and 7, is the most formative influence on the structure (way it is written and organized) and content (the teaching being communicated) of John's Revelation.

Daniel and Revelation both teach: Suffering, final victory and reign of Christ and his people.
                                                       Conflict with Satan and his evil forces which ends in judgment

As far as the "fourth animal and the horns" go, quite frankly, I too am a bit puzzled. More study and research are needed.

My most straight forward reading of it would lend me to see the four beasts representing four earthly kingdoms (Babylon, Media-Persia, prehaps Greece, and Rome). However, regardless of who they are exactly, one thing is overwhelmingly clear, these kingdoms are opposed to God's heavenly kingdom and to him as King.

Similar, by the time that we get to Revelation 12-13 we find that the "dragon" figure takes on the imagery of the kingdoms of Daniel 7 as also "coming from the sea." This dragon is most likely identified in the first-century context as one of the evil kingdoms prophesied in Daniel, namely, Rome.

Yet we also know that the "dragon" is not only a metaphor for Rome, it is also a reference to Satan himself who stands as the representative head of all evil kingdoms (Rev. 12:9, 20:2). Thus, once again, we see the consistency of the picture painted by both Daniel and John. That picture being:

The devil is the force behind all the wicked kingdoms of earth who persecute God's people and seek to oppose God as King. The Lord's people are going to be persecuted by a beast that will pursue them even unto death, there will be much suffering endured by God's people. However, Satan will not succeed against the Kingdom of our God, rather God will execute vengeance upon his foes with great finality, deliver his people, and "the kingdom of the world will become the kingdom of our God and Christ and he shall reign forever and ever" (Rev.11:15 cf. Rev.20:10).

Hopes this helps,
Pastor Adam