[GeorgeDewar]

I can help with number 2.

Two transactions are happening at the same time. Your "sales" revenue account is going up (Credit) by $2 and your cash asset account is going up (Debit) by the same $2. That is the first balanced transaction.

The second transaction is that your inventory asset account is going down (Credit) by $0.50 as you have less inventory now, and an expense account called "Cost of Goods Sold" is Debited by the same $0.50.

Your profit gets calculated on demand. There are two ways to do it, both yielding the same result. You can look at revenue minus expenses over a period, giving $2 sales minus $0.50 cost of goods sold = $1.50 profit for the period. Or, you can look at how your equity (assets minus liabilities) has changed over that period. In this example, no liabilities have changed and your assets (bank account) have increased by $1.50 because bank has gone up by $2 while inventory has gone down by $0.50.