Back twenty or thirty years ago, there were several viable interpretations of the parable of the fig tree.
1948 +40 years = 1988 (fail)
1948 +70 years = 2018 (fail, because the 7 years comes first)
1967+40 years = 2007 (fail)
1967+70 = 2037 this is the right combination. Jerusalem is the fig tree because as Jesus and the disciples were about to enter Jerusalem, he cursed the fig tree beside the road, knowing that them in Jerusalem would reject him. So when the Jews regained control of Jerusalem, in 1967, that is the base year.
2037 is at the latest, could be much sooner than then, but not without the 7years taking place before it. The 7 years are going to begin when the person who becomes the Antichrist confirms the Mt. Sinai covenant for 7 years - as Moses made it a requirement for all future leadership to do likewise of him being the first to confirm the Mt. Sinai covenant that God gave the children of Israel the land of Israel as theirs forever.
What the confirmation of the covenant will look like will be a big speech by the Antichrist on the temple mount to the nation of Israel, like Moses gave in Deuteronomy 31:9-13. Won't happen until after Gog/Magog, to end the muslim presence on the temple mount.
Biggest issue with your approach is one-trick nature of it. At least for me. You have two numbers, you add them, and voila, we've got a year. I think you make it extraordinary simple, completely opposite to the nature of God's end time prophecy.
Not to mention other problems.
For example, Israel, or Jewish nation, is fig tree per parable of the barren fig tree in Luke 13:6-9. Jesus did curse fig tree in Jerusalem, but He had to curse it somewhere. Had He cursed fig tree in Bethsaida, would you think that fig tree is Bethsaida? It doesn't mean fig tree isn't Jerusalem, but I think it's primarily whole Israel.
Generation is noted as 70 or 80 years, with today's Jews in Israel living somewhat longer than 80 years on average, so 80 could be the number of generation. Or maybe even 82, since that's current life expectancy in Israel.
Also, Jesus says "generation will not pass" not "full generation will be completed" or something like that. Meaning, Jesus doesn't say that one full generation has to complete, but that it will all happen within one generation. So, number for calculation might not be either 70 or 80 or 82. It might, but also it might not.
So not only do you have a problem by simplifying it to one simplest calculation (a+b=c), your one calculation is arbitrary in nature.
Now, if fig tree is actually Israel, and if generation is 82 years, then we have 1948+82=2030 as last possible final year. But what does this calculation mean? Not a lot, since I am not sure if either 1948 and 82 are correct numbers to calculate. We are in the season, but since we are so close, arbitrary calculations (not to mention one-trick-natured arbitrary calculations) can end up to be very misleading.
