70 minutes at FRA is not unrealistic; it is pretty standard LH connecting time. As mentioned before: MUC (which is a better airport for LH/LH connections) has a minimum INT/INT connection time of 35 minutes. LH is very good at connections, and as long as you are on one ticket they will take care of the connection. FRA has very long walking distances if you are unlucky, but if you are close to missing your connection, dedicated staff will wait for you at the door of your arriving flight, and accompany you to your connecting gate. They will drive you there if necessary. Should you miss a legal connection, they will put you up at an airport hotel (often the Steigenberger, five minutes away), and feed you until the next flight out.

I would also guess that the India-flights of LH have a pretty high number of connecting passengers from the US, meaning that it might be worthwhile for LH to hold the BLR-flight if the LAX-flight is late. The negative consequences of waiting for connections on a longdistance flight would be less than on a US domestic flight, especially as I presume BLR very much is a O/D airport (unlike CPH which for SK very much is an international hub)

In short: I would not hesitate to book a 70 min LH/LH-connection at FRA