Thanks brother Sam, that you have made an effort to search explanations for the quoted verses. Explanations come in different hue and cry. Explanations depend upon not only on what the author of the opinion believes and favors, but also on his vested interests. The word of God is everlasting. You have quoted Martin Luther saying “Martin Luther suggested that “the signs here spoken of are to be used according to need. When the need arises, and the Gospel is hard pressed, then we must definitely do these signs, before we allow the Gospel to be maligned and knocked down.” Good, but Martin Luther has not realized that the decision to work signs is not vested in the hands of the believer; it is the Holy Spirit and none other than the Holy Spirit can ever decide when to work these signs.It is also abundantly clear that Martin Luther has not understood what these signs really demonstrate. The Holy Spirit is continuously manifesting the signs in every believer’s life. Consider the following:
Mar 16:17 And these signs shall follow them that believe;
In my name shall they cast out devils;
This is grossly misunderstood to mean that every true believer got to be an Exorcist or a Sorcerer. That is not true. Devils do tremble before the Lord Jesus Christ. They fall prostrate before Him. Devils are cast out by the Power and on account of the presence of the Lord in a believer. So the sign is only an affirmation of the Presence of the Lord in a believer.
they shall speak with new tongues;
The new tongue doesn’t mean a different language or an unknown language or some meaningless unclear utterance. It simply means that the Holy Spirit will reveal the mind of God to the believer enabling him pray in accordance with the Will of God and also rightly divide the word of God. It doesn’t make him a futurologist or a fortune teller or a special emissary of God or a prophet.
Mar 16:18 They shall take up serpents;
This sign is a sign of Strengthand Courage constantly provided to the believer. Serpents signify Satan and his associates. A true believer is constantly and eternally strengthened in their warfare, enabling him to take on the enemy with an assurance of victory.
and if they drink any deadly thing, it shall not hurt them;
This sign is indicative of the protection that the believer is assured of. A true believer is protected from falling into any and all machinations of the enemy. Deadly things are those that can kill the soul or quench the spirit.
they shall lay hands on the sick, and they shall recover.
It doesn’t mean that every believer will be an exraordinary super-specialist physician. A believer will intercede for the sick in the name of the Lord and the Lord God who has the authority to forgive sins, may remove the root cause of the sickness i.e. the sin by granting forgiveness of sin which in turn will result in healing of the sick.
You also said “Mark did not say that the miracles would continue. The words “to the end of the age” are not found here as they are in Mat_28:18-20.” Matthew was speaking the assurance given to the disciples that the Lord shall be with them to strengthen them in their work unto the end when He said “lo, I am with you alway, even unto the end of the world.” That has no relevance to the signs that manifest in a believer. The believer in the days of the Apostles is in no way different from the believer today or in the days to come.