You cannot modify STP hello timer only for one port - it is timer for whole STP tree. Also this modification wil not help you - because if you have drops on this long link, you will have problem with STP anyway.
What you need to do?
If you have only one link, you can turn off STP for the both side for this link and split STP to two domains (one domain per site). You can do this by "bpdugilter" on the both sides of this link. In this case you can also implement a storm-control\any other protection for this link to be sure that problem in one site will not propogated to other site.
If you have two links between these places (for redundancy), you definitely need to avoid any L2 protocols between them. You need to implement IP routing and then, if you need Ethernet between two segments in the different sites, you can implement tunneling.
My experience say me, that the best answer in such case is MPLS, but maybe you cannot do this due to budget/equipment limitation.