"How much of a penalty can I expect if I exceed the time by a couple of days?"
First, there should be no Form 1099-R if the JPMorgan Chase properly initiated a trustee-to-trustee transfer of the IRA. This is not any kind of rollover. For a proper trustee-to-trustee transfer, they would have made the a check out to a traditional IRA for your benefit, not to you personally. There is no time limit on completing a trustee-to-trustee transfer because there is no distribution.
However, if the funds somehow get paid to you, it becomes a distribution. The 60-day clock would start on the day that follows the day that you have constructive receipt of the funds.
Since you already have the IRA at Corebridge that was intended to receive this transfer, why not just have them deposit the funds into that account and complete the transfer (not as a rollover contribution)? If you instead receive the funds and deposit them into another traditional IRA, you will likely have to report it as a distribution and rollover by submitting a substitute Form 1099-R (Form 4852) because it seems that nothing about this will result in a Form 1099-R issued by either JPMorgan Chase or Corebridge.
