What could be the problem with this TLS 1.2 Client Finished Message approach?
The sequence_number resets at CCS, so for Finished it's zero (for 8 bytes). Also record type for handshake is 0x16, 
and to be clear the record length is 2 bytes, in this case 00 10, and "the IV" should be random for each record.
As a mnemonic, the RHUL group's Lucky Thirteen attack uses the fact that the HMAC pseudoheader is 13 bytes. 

That said I agree with @Maarten's comment: debug against another implementation. Especially an open source one like OpenSSL/LibreSSL/BoringSSL or GnuTLS or Java.