Rescuing contaminated home made jam - possible?
One thing to remember with food safety is that questions like "is my food safe/contaminated/edible" can't be answered with a simple yes/no. There's no way to be certain if eating a given food will without question make you sick; even if you were to sample and test for bacteria and toxins, you could simply have missed a contaminated portion, or there might not be enough of a contaminant to make you ill. Conversely even food prepared as safely as possible can be contaminated immediately by bacteria in the air.

All you (or anyone) can do is determine how preparation affects the probability that food has a chance of making you ill. In commercial/professional settings, there are known-good, legally-enforced standards for practices that promote low levels of risk and avoid the potential for serious contamination (which still vary by country and setting!) At home, no such standards exist - there are guidelines, yes, but you as the person eating or serving the food have to determine whether a given level of risk is acceptable to you.

So - all that said, concerns around chicken usually center on salmonella or e. coli, two bacteria that are relatively common in chicken (due to factory farming practices) and which can make you seriously ill. Both are destroyed by sufficient heat, which is in part why we're instructed to thoroughly cook chicken; they can also spread easily, which is why cross-contact with raw chicken should be avoided. Once chicken has been cooked and the pathogens killed, it doesn't present the same level of risk. It sounds like that's the case here; a spoon used for basting would mainly come into contact with (very hot) basting liquid, and perhaps the (very hot) outer surface of the roast chicken. So there's not the same level of risk as if your partner had used, say, a pair of tongs used to handle the raw chicken.

A properly prepared jam is also not terribly susceptible to contamination. Even though it's largely sugar, there's so much sugar that it "locks up" most of the available water; there's not enough free moisture for bacteria to thrive. The exception for jam is if you're canning it for storage at room temperature. In this case a much higher standard must apply; long-term storage provides ample time (and the right temperature range) for even small amounts of contamination to grow to hazardous levels. For canning, just about any deviation from a known-good recipe must be regarded cautiously, including incidental cross-contamination.

Some other things to consider are possible high-risk individuals who might eat your jam. For people with compromised immune systems or other conditions, even generally harmless amounts of contamination present an elevated risk. If either you or your partner have an immune deficiency or are pregnant, exercise greater caution. The same applies if there are small children or elderly adults who will be eating your jam. You should also consider allergies; an adverse reaction to chicken itself isn't that common, but it is possible, and allergic response can be triggered by very small amounts of incidental allergen. Anything that was in your braising liquid could now be present in very small amounts in the jam.

Overall, I wouldn't say that this presents an egregious or unmanageable risk. If you don't have health reasons to be specially cautious, and if you keep the jam stored in the refrigerator, it probably presents a relatively low risk. I wouldn't advise canning with it, nor breaking up with your partner over an honest mistake. In the end, you must determine for yourself whether this is sufficiently safe to justify the small potential risk that the accidental cross-contact introduced.