Always hold majority of your fund in btc rather than altcoin as btc is dominant one and other follow its trend so if there will be rally then sure btc will ride but when it reaches certain point altcoin will follow it. So my best advice is to make 70:30 or 80:20 btc to altcoin ratio to get safe ride in having duration.
Not really, if you see ETH in the past month, it has a nice bump over bitcoin. From 0.019btc to 0.028btc. So, if you chose the right coin, you can easily multiply the number of bitcoins you have.
And about the halving, i think the best moment to sell is a couple of days it happens.