If this is his temperament, then you may want to point him towards knowledgeable stock advisors. Talk to him about keeping an emergency fund, talk to him about having some conservative investments, and not all speculative. Chat about quality, dividend producing companies that have a long track record of increasing dividends.
Maybe your dad does not want to be an index investor, and that is OK, it is his money. Just encourage him to be careful with it.
This is something that interests and excited him and that is OK. Encourage him to hold his companies long term and not be a trader. Wealth comes from long holding periods of quality companies. I personally love Jim Cramer, caution - he covers a LOT of stocks - but if you focus in on his favorites and the things he has in his charitable trust, those are good solid companies.
Which newsletters is he into? Point him toward Jim Cramer's podcast, book Get Rich Carefully, and The Motley Fool Stock Advisor, Income Investor, and Options/Pro (I use Pro as my main advisory service and those guys are smart/successful/disciplined). Try to get him towards stocks that are maybe a little boring, but they aren't going to go broke - Berkshire Hathatway, Wells Fargo, Starbucks, Johnson & Johnson, Disney, Under Armor, etc. If he wants to buy oil, he should buy a BIG oil company, like XOM. They aren't going to go broke. Always focus your discussions around company quality, and holding on to his investments and not hopping from one stock to the other.
It could be a lot of fun to talk stocks with your Dad. Do your best and enjoy the experience with him.
If he is talking a lot, that is OK, if he is trading a lot, that is not so great. Especially with a portfolio where there is no new money coming in, he needs a portfolio that will generate income and appreciation. He needs a fairly conservative portfolio.