There is no reason to have a lithium level as you don't take lithium. We normally don't have lithium in our systems. "Permanent" - all bipolar is permanent, there is no cure, only medications that can help control it. It is great that lithium stabilizes your father.
As to your situation, yes, you could develop bipolar since it has a genetic component. With some people it just starts and with others there is some triggering event that sparks it. Good living (exercise, sleep) is always a good thing but it won't keep bipolar from starting if you are going to get it. Since you get your genes from both parents, then you probably have 25% or less chance of getting it. If both parents have bipolar then you have a 50% chance of having bipolar.
Those percentages are not entirely correct. It's true that if bipolar disorder was 100% always inherited by children from their parents then you would have a 50/50 chance of getting it. But nobody knows all the factors involved in getting a mental disease like bipolar disorder. I don't have the real stats on hand, but the actual chances of getting bipolar disorder if one parent has it are much lower than 25%.
The fact that it can be triggered by stuff seems to be true based on how many people have reported it, but nobody knows why or by what except in cases of what we know already are toxic chemicals. It can also be found to be related to other people in the family having problems with anxiety or depression, but that is also pretty up in the air. You can't get bipolar disorder like you can get Alzheimer's so there isn't anything you can do to prevent it (from what we know so far).
In any case, most people who experience bipolar disorder show symptoms for the first time around their teen years. If you're already older than that you're well outside the range of people who might get it.