Isn't Bull Put Spread's Maximum Loss = Spread Credit + Loss from sold call + Profit from bought call?
You have your minus signs mixed up for buying and selling the underlying.  When your short call is exercised, you sell the stock for 44 (credit).  When your long call is exercised, you buy the stock for 48 (debit). So in your terminology, the maximum loss  is:

(-P + 44) + (P - 48) + spread credit = 44 - 48 + 3 = -1

A much easier way to remember this is that with vertical spreads:

If it's a credit spread, the maximum gain is the credit received and the maximum loss is the difference in strikes less the credit received.

If it's a debit spread, the maximum gain is the difference in strikes less the debit paid and the maximum risk is the debit.