Hi Kevin, 

All great questions and thank you for contacting AskExtension. 

1. There are a few companies I am familiar with that have their own local seeds.  Ohio Heirloom seeds, Schlessman in N Ohio and Merit seeds in Berlin. Sometimes the local seeds savers can help you find seeds for your area. Everyone has their favorite seed companies and most companies can tell you if their plants will be successful in your zone. 

2. In reference to your zone question, the USDA is  responsible for determining the zoning map. It is an average of the past 30 years. It is possible you are seeing maps from different years that have been redetermined. The additional a,b has been added to further divide a zone based on low temps averages for microclimates. Example 5a, lows are -10 to -20,  5b -10to -15 degrees F . I think this is important for large fruit production and landscaping plants. A vegetable gardener would know need to know frost and freeze dates specific to your zone. 

3. Regarding succession planting and companion plants, below is a  link to the Stark co  MasterGardener  information. I believe they have a garden planner. You can also sometimes find specific planting calendars through different seed companies. I use one from Vermont bean and seed. It is free and they send you reminders of what needs planted by your zone. 

https://stark.osu.edu/program-areas/agriculture-and-natural-resources/community-gardening-resources

https://stark.osu.edu/program-areas/agriculture-and-natural-resources/grow-your-own-food

https://wayne.osu.edu/sites/wayne/files/imce/Program_Pages/ANR/Garden/Planning%20and%20Planting%20%20the%20Garden.pdf

https://mansfield.osu.edu/events/plantingcompanion021420.htm

4.  I am not familiar with how successful solar electric fences are for keeping deer out of your garden area. I did find an OSU article about using electric fence for sheep. AskExtension has asked the volunteers not to refer people to .com research. but there seems to be a great deal of information about solar fences for gardening. I think the question is how much you want to spend. 

https://u.osu.edu/sheep/2021/10/05/electric-fencing-for-sheep/

5. Information about vine length and squash sizes is very specific to the variety that you choose. If you have a smaller area, it is possible to find seeds for a variety that will not grow more than 10-12 feet. Some varieties come both in vine and bush, but normally the rule of thumb is summer squash is a bush, and winter squash is a vining plant. 

https://ohioline.osu.edu/factsheet/hyg-5530

http://www.gardening.cornell.edu/homegardening/scene6420.html

I gather from your questions that gardening is in your future plans! Good luck and I hope you enjoy it as much as I do.  Stark County has a very active Mastergardener group that can provide a wealth of information as you proceed. My local group from Washington County  has a presence at the Marietta farmers market each Saturday. I am sure in your county they provide similar support. Contact your County extension office and they can  help you find local support.