1000kg is not little, but it's definitely not a massive amount either. Well, technically he could stuff an average Kei car into his dimensional storage, but naturally he wouldn't.
"I'm 35" doesn't the summary call him 38? Unless he's lying for some reason but why bother for a 3 year diff lol (i guess he brings it up in his thoughts the next few pages but other than it usually being the expected 'cutoff' from onii-san to ojisan it seems like not that big of a gap to a teenager versus someone claiming to be 10 years younger, altho i'd think going thru shit in the isekai world would make him age a decade more lol)