Ex-MSNBC host Tiffany Cross learned that she was getting pushed out days ahead of her exit — and threatened to “go out in a blaze” and “take down” the cable-TV network and its boss Rashida Jones, The Post has learned. The controversial anchor — whose weekend show “The Cross Connection” was abruptly canceled earlier this month as MSNBC elected not to renew her contract, according to sources — began frantically calling other journalists, media executives and social activists a week before her ouster in a bid to rally support, a source with knowledge said. “She made calls saying: ‘I’m going...