Yes - you may use Turbotax - but need a business version - see here -
I am not sure what "complications" do you mean - if you want to do tax filing on your own - there is nothing wrong with that - but you need to educate yourself.
I still suggest to have a tax professional to verify your filing before sending to the IRS.
I was told - In order to avoid audit, one must pay oneself a salary by taking a loan even if the corporation is not making any money - is this true?
That is correct - the IRS expects that the S-corporation pays you a reasonable wages for services you provided for the S-corporation, however - as long as your S-corporation has no income - you S-corporation is not required to pay wages to owners.
I have spent about $600.00 in incorporating my two businesses 6 months ago, now weighing the benefits and losses from your knowledge please let me know if it is okay to convert them into sole-prop?
Generally - startup costs will have to be written off, or amortized, over 15 years. However if you close S-corporation all start-up costs related to creation of S-corporation may be deducted.
I have this basic knowledge of filing taxes - do you think I will be able to file my taxes successfully with turbo tax software?
All tax filing are done by people who learned that business and are improving the knowledge. You may learn as well, however as you do not have experience - while not required - it would be wise to have a tax professional to verify your filing before sending to the IRS.