Furthermore, do you ever hear of anyone having their wages garnished in some kind of a lawsuit that would have been prevented with an umbrella policy?

I believe it tends to give me a slightly lower return, because the sponsor is going to be more careful, and if there is a severe downturn will prevent me from taking catastrophic losses.

Then the plumber went in and could not repair the clog in the toilet and had to replace the toilet and all the faucets in the house!!

You have to consider increased water bill, and if you pay utilities, increased gas/electric, and also increased clogged plumbing.

Thanks for telling me because it prevents me from stepping in too early and making a mess. 

The tenants still have power in the unit (i.e. other appliances and outlets are all working), but I don't want to neglect this and create a situation where a fire hazard may be present.My question is: is there any type of preventative maintenance (i.e. periodically add deox/other chemicals to support conductivity) or inspections I should be doing as landlord on the panel every so often?

You can set a reserve to prevent it from  going to cheap or at a loss. 

If you already have income and are eligible to buy real estate; your DTI will not prevent you from acquiring a house if you are purchasing a cash-flow positive investment property.

A favorite trick of sellers is that for one or two years before they put their property up for sale they stop doing any preventive maintenance, and only do the repairs that are absolutely necessary, in the cheapest way possible.  

One big key you left out that will prevent anyone from giving you accurate input is, what will the unit rent for each month?