We are sorry to hear of the loss of your husband. With regards to the uninsured motorist bodily injury portion of your auto insurance policy first the accident would need to fall under this coverage, meaning that an uninsured motorist caused the accident which killed your husband. If this is the case then your UM BI would pay up to the limit of $300,000.
It does not mean that for certain you would get the whole $300,000 but that is the limit that the policy would pay for one person injured or killed in one accident. The $500,000 number represents what the UM BI limits would pay for all persons injured in an accident. For instance if you were also injured as a passenger in the vehicle with your husband then the most you could collect for all injuries to both you and him would be $500,000.
UMBI covers you, the insured members of your household and your passengers for bodily/personal injuries, damages or death caused by an at-fault uninsured or hit-and-run driver. If you are involved in an accident where the other driver is at fault but has no insurance, your policy will cover your medical expenses, up to the limit on your policy. So if your husband's claim will be the only one going against your UM BI $300K would be your top limit but as we mentioned you may not receive the whole amount.
To find out how much of a settlement you would receive after your husband's death from your auto insurance carrier you would need to discuss the claim with adjuster assigned to your case. Any medical bills for your husband, etc relating to the accident would need be discussed as part of the settlement negotiations.