Yes, that's close enough in meaning. I don't think we have that as an accepted answer anywhere yet but I'll try to add it in some places.
You can hear people say dränerande in Swedish when they want to say exactly this, it's an anglicism but it is used. Old Swedish words with a similar meaning would probably be utmattande, slitsamt, nedbrytande etc. Or you say it in roundabout ways like det suger musten ur en.
I don't really think it makes sense to call one living language older than the other, as they all evolve daily. Both are Germanic languages and both got a bit Frenchified/Latinized for historical reasons. I think North Germanic started becoming unintelligable to West Germanic 1800 years ago, after three centuries of Germanic tribes spreading outward from what you would call Southern Sweden.
- jobbig is the adjective for singular en-words, like en jobbig dag
- jobbigt is the adjective for singular ett-words, like ett jobbigt år
- jobbigt is also the adverb form, like han gjorde det på ett jobbigt sätt
- jobbiga is the adjective for plurals, like två jobbiga dagar
In this case, since you have det, you need the ett-word form.
Also in response to your question on pronunciation, the g is usually silent in jobbigt, but the t is always pronounced.
Tiresome is the preferred translation of jobbigt. I am wondering about the exact meaning of jobbigt. Tiresome can mean boring OR annoying. Since "jobbigt" was applied to "hennes barn" in another sentence, I'm guessing it doesn't mean "boring" but more like annoying and tiring. Is this right?
I refer you to the first hit on Google just now: https://www.google.co.uk/search?q=synonyms+for+tiresome&ie=UTF-8&oe=UTF-8&hl=en-gb&client=safari
Google shows different top results to different users, so I don't know for sure to which result you are referring. My top result is for thesaurus.com, which despite its name is generally a really bad resource for determining synonymity, presumably since it makes money out of always presenting synonyms whether words are actually synonymous or not.
Either way, I'm not disputing that boring and tiresome share senses. I'm only disputing that they share this specific sense. Sure, you could easily imagine an annoyed teenager going "Mooooom, it's so boooooring!", eyes rolling, but that'd likely be translated into Swedish as tråkigt every single time by every single native Swede. If you say jobbigt about something, it's either explicit or implied that it exhausts your energy - mental or physical - in some way. I really don't think boring covers that.