There's a reason Bitcoin is the safest asset to invest in, the crypto market is highly volatile, It's very difficult to predict the trend of these Altcoins and that's why the safety of your investment isn't guaranteed when you choose to invest in Altcoins. But investing in Bitcoin gives you more assurance because you know that even in the next 10, 20, 40 years to come, Bitcoin will still be there and reaching new heights, but Altcoins can't guarantee you such assurance.

And regards to planning your DCA. You don't need to have any specific amount in mind to DCA, just put in a particular amount from your weekly, or monthly income, don't know how much your income is so I can't tell you how much to DCA. But just like saving in a piggy bank you can make your evaluation and then come up with a reasonable amount, but what's important is being consistent in whatever amount or percentage you choose.

Look for the reasons that make you invest in altcoins, and you will find that most of them are related to quick profits that will not happen. Therefore, it is better to stick to Bitcoin, especially since you are not just betting on profit, but rather you are betting that the loss will be less than the loss in altcoins, and the profit will be reasonable.

Buy a little bitcoin a week and study in depth the dynamics of the cryptocurrency market cycle, knowing this in two complete cycles will give you the ability to change the reality of your life

and most importantly don't mess with shitcoins

Theres nothing wrong with the agenda you have because you know the reputation already of bitcoin so people would like to make a safe haven here but again don't put all of your assets in just a single pocket or basket, and again as you are saying that the bitcoin is like the mother of all coin and you know when the price of the bitcoin moves the higher chance that the other coins will move to it's a good choice still or instead seek another coin which is paired to BTC. Make a plan for what you want to do with your bitcoin so your not just get confused with your actions.

If you are more confident in bitcoin then continue your plan to keep doing the DCA strategy whether it's doing it every week, every two weeks or once a month depending on your ability when you have money to spend on bitcoin, I think it's better once a week so that the accumulation of bitcoin will grow faster than what is expected but even that must see how your cash flow is so that it does not become an obstacle in the future.

Altcoin is always tantalizing when the price of the tide is rising but you should not be complacent because it could be a trap and they throw it into the market, this kind of thing often happens especially if you are pessimistic about altcoins then never invest it is much better if you doubt it.

You have a mature mindset on crypto assets as a whole, Investing in Bitcoin is much safer compared to Altcoins. You have outlined some of the suggestions yourself in Op, if you think Bitcoin will reach its highest price, then why should you think about other investments besides Bitcoin. You can use the DCA strategy depending on the money you hold, if you have a daily income, you can buy Bitcoin every day according to the amount of money you have and likewise if you have an income every week or every month.

Now you just need to feel how good it is to benefit from the investment you make with Bitcoin.
The increase will make you even more eager to continue holding until the target price is reached.

About what mindset you should have, it depends on how you live it.
If you're already convinced, you just need to add some Bitcoin holdings.

Doing DCA is the best strategy, prepare your reserve fund and do DCA so that you will get cheaper prices later.
Make sure you do it regularly, determine the time range you need to do DCA.

You cannot stop these meme coins from seeing them skyrocket, but rest assured they will never stay up all the time. Just like with bitcoin, it has it's own time to rise and drop at some point. But knowing bitcoin is the king of crypto, that fact guarantees that bitcoin is the most secured and profitable coin in the crypto market. Bitcoin gains the trust of the majority, so you should prove it to yourself as well.

However, I would not advise you to stick with bitcoin but do your own diligence to research. That way, at least you will decide on your own based on what you have learned about bitcoin.

Just think that bitcoin is designed for long term investment that makes a high promising return. While altcoins are just recommended for short term as most of them are for quick profits, wherein majority do not realize those quick profits. If you can analyze it smartly, then you will know that bitcoin makes a wise investment.

If you decide to leave bitcoin, probably you saw some lapses that some of us are not aware. But frankly speaking, leaving bitcoin could make you regret your decision, as altcoins are not actually even worth keeping.