I agree Sandra Jean with your first statement where you said:

You asked, "Why guess a Jewish holiday for the rapture of the mostly Gentile Church?"  For the simple reason found in the following Scripture: "But if some of the branches (Jews) were broken off, and you (Gentiles), being a wild olive, were grafted in among them and became partaker with them of the rich root of the olive tree...." (Romans 11:17 NASB) 

However, I can't see that Gentiles are to keep the Laws regarding Feasts that God commanded the Jews to Keep.  You quote Deuteronomy 16:10-11,14-16 and those are very specific with respect to the stranger or Gentile person; they speak of the Gentile "living among us," and "Those that are living among us."  I haven't read the previous chapter, but this chapter doesn't reference all the feasts.  You can review the scripture you quoted below, but to get a clearer picture read the whole chapter.

And thou shalt keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the LORD thy God, according as the LORD thy God hath blessed thee: And thou shalt rejoice before the LORD thy God, thou, and thy son, and thy daughter, and thy manservant, and thy maidservant, and the Levite that is within thy gates, and the stranger, and the fatherless, and the widow, that are among you, in the place which the LORD thy God hath chosen to place his name there.  Deut 16:10-11

And thou shalt rejoice in thy feast, thou, and thy son, and thy daughter, and thy manservant, and thy maidservant, and the Levite, the stranger, and the fatherless, and the widow, that are within thy gates. Seven days shalt thou keep a solemn feast unto the LORD thy God in the place which the LORD shall choose: because the LORD thy God shall bless thee in all thine increase, and in all the works of thine hands, therefore thou shalt surely rejoice.  Three times in a year shall all thy males appear before the LORD thy God in the place which he shall choose; in the feast of unleavened bread, and in the feast of weeks, and in the feast of tabernacles: and they shall not appear before the LORD empty:  Deuteronomy 16:14-16

You also say: "Leviticus 23:1-2, 4 tells us very clearly that these are festivals of the L-rd." I didn't go back and read it again, but I'll take your word for it.  If I asked you to whom was the law given?  you'd have no choice but to reply "to the Jews."  Why would God give the law to the Jews commanding them to keep it and expect it to be kept by Gentiles?

Another point to consider might by since we are now under grace, and not under the law, then why would the Jew who is saved, place him or herself under the law?

Reference: Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.  But after that faith is come, we are no longer under a schoolmaster.  Galatians 3:24-25

So referencing the verse you first quoted, we did not become attached to Judaism, but to the root Church which was created at Pentecost and mainly made up of Jews.  You cannot attribute things that God said specifically to Jews in the Old Testament to the Church, which didn't even exist at that time, which is made up of both Jews and Gentiles.  We are under grace and not the law, and the purpose of the law to the unsaved remains the same as spoken of in the Galatians verses above; "To bring the unsaved to Christ."

The reason for the unsaved Jewish people to continue keeping the laws regarding the feasts is for their benefit to ultimately bring them to Christ in the redemption period (Tribulation).  God has a plan of redemption for ALL Israel, which He is just about to implement.  So, when the rapture occurs, it will be perceived as a Gentile event, and having it occur on a Jewish feast day would just confuse the Jews not enlighten them.  Those Jews whom God has chosen to lead in the redemption period will know the meaning of the feasts and their ultimate fulfillment, both in the past, and to them, in their near future.

The Jubilee event which will occur in the year 2017, I think is likely to happen on the feast of Yom Kippur, the Day of Atonement.

Reference:  And thou shalt number seven sabbaths of years unto thee, seven times seven years; and the space of the seven sabbaths of years shall be unto thee forty and nine years.  Then shalt thou cause the trumpet of the jubilee to sound on the tenth day of the seventh month, in the day of atonement shall ye make the trumpet sound throughout all your land.  And ye shall hallow the fiftieth year, and proclaim liberty throughout all the land unto all the inhabitants thereof: it shall be a jubilee unto you; ...  Leviticus 25:8-10

I think Pastor Riley and others who have considered this event as potentially being fulfilled by Christ Himself as He returns WITH His saints at the end of the Tribulation quite possibly have it right.