What i would have done..
I thought this was a highly enjoyable show even though it does have a few loopholes and flaws but no show is perfect.Below are just a few stupid ideas on what i personally would have done in Jakes position. Im not suggesting in any way that Mr King should have done these because hes a genius writer and im not and my ideas wouldnt be good tv lol.
I think if it was me the first thing i would have done is win a large amount of money on sports betting and possibly investment. Move from city to city so as not too arouse any suspicion. I would have gone to Bills Home town and offered Harrys mum a large amount of money to take the kids and run. She seemed to me like she'd be fairly receptive to it. You could even consider offering Frank a large amount to leave and never come back. Worst case scenario is you kill Frank and dispose of the body somewhere it will never be found. Take a gun with a silencer and predig a grave the night before.
Then id go and get to know Oswald and as quickly as i could try and convince him to come to Maine. Flash some cash, tell him you love Marx, Tell him your meeting with some big influential communist friends there. As soon as your there shoot him and hop back through the portal. You would see then if he was involved in the Kennedy shooting and what the result of stopping it would be. Based on what happened in the show he would have seen that Oswald was the only person involved and that the world had gone to hell by killing Oswald. So hop back in and reset.
Then finally i think id go back and find things from 1960 that are now considered valuable today and just collect them up and bury them in a box for me to find after i go back to the future. If you could somehow invest in stock you know that would be successful and claim them as yours in the future that would be even better
The annoying thing would be that you'd have to sort out the Frank situation every time you went back so you'd want to limit the number of times by good planning. Then when you've finished, buy the diner and brick up the portal.
Of course all of this would depend on how time viewed these changes and decided to push back.