I will do the best I can to give you my thoughts on the little horn- although I don't claim to understand every prophecy. A horn is a kingdom or king according to Gabriel in Daniel.
Daniel 2 and 7 describe the same series of kingdoms, 3 of which are named in the book of Daniel:
Babylon, Medo-Persia, Greece, Rome.
History gives us the dates:
Babylonian Kingdom 612 BC – 539 BC
Medo-Persian 539 BC – 331 BC
Greece 331 BC – 168 BC
Roman Empire 168 BC – 476 AD
Revelation 13 describes a beast that is a composite of those 4 kingdoms. This is an important connection and helps to identify the antichrist that came from those kingdoms and retains traits of each.
Western Rome fragmented into 10 kingdoms (10 toes of Daniel 2, 10 horns of Daniel 7). Modern names in parenthesis:
Allemani (Germany), Franks (France), Burgundian (Switzerland), Suevi (Portugal), Visigoths (Spain), Lombards (Italy), Anglos Saxons (England), Heruli, Vandals, Ostrogoths.
The last three are extinct because they were uprooted by the little horn power.
The little horn power is the same blasphemous power that claims to be equal to God and sits in the temple of God.
The temple of God is not a physical temple. Jesus said it was left unto you desolate. The kingdom of God is a spiritual temple made up of people: Jesus is the chief cornerstone, the foundation are the apostles and prophets, we are living stones (Eph 2:20, 1 Peter 2:5, many others.) [A third physical temple with animal sacrifice would not be a temple of God it would be blasphemy against the true Lamb of God]
So, this little horn is a civil power that uprooted those three kingdoms, claims to be God, sits in the spiritual temple of God, seeks to change times and laws, has the number of 666, had a deadly wound that was healed, and made war with the saints for 1260 days (years) [538AD-1798AD]
There is only one power that fits all of the specifications and all of the Reformers agreed who this is.
quotes from this power:
“We hold upon this earth the place of God Almighty.”
The Great Encyclical Letters of Pope Leo XIII, p. 304, June 20, 1894
“The Pope and God are the same, so he has all power in Heaven and earth.”
(Pope Pius V, quoted in Barclay, Chapter XXVII, p. 218, ” Cities Petrus Bertanous”)
“The Pope is of so great dignity, and so exalted that he is not a mere man, but as it were God and the vicar of God.”
Ferraris Ecclesiastical dictionary
“The strong and effective instrument of salvation is none other than the Roman Pontificate.”
Pope Leo XIII,
Allocution for the 25th anniversary of his election,
February 20, 1903
Here is a detailed presentation on this: