Insterstate SRM-27 is a lead acid.
Using the alternator with the amount of power consumption your using won't get it. You're drawing more amps than what is being put back in.
The house generator or Honda, running through your convertor won't either, assuming the convertor is original.
A second battery will help, but doesn't solve the real problem. If you don't have enough power to run / charge the Mac Book that is bad.
The Honda in conjunction with a portable battery charger, connected directly to the battery is much better.
As mentioned above, venting lead acid is mandatory, no matter what you decide. I lean towards two 6 volts in series & using the Interstae as a back-up, depending on the distance of cable runs, 6-8 gauge wire
